├── go.mod ├── go.sum ├── node_chain ├── node_chain.go └── node_chain_test.go ├── linked_list ├── enumerator.go ├── linked_list.go └── linked_list_test.go ├── .gitignore ├── avl_tree ├── avl_tree_test.go └── avl_tree.go ├── graph ├── graph_test.go └── graph.go ├── README.md ├── queue ├── queue.go └── queue_test.go ├── dijkstra ├── priority_queue.go ├── dijkstra.go └── dijkstra_test.go ├── stack ├── stack.go └── stack_test.go ├── heap ├── heap.go └── heap_test.go ├── sort ├── sort_test.go └── sort.go ├── binary_tree ├── binary_tree.go └── binary_tree_test.go └── LICENSE /go.mod: -------------------------------------------------------------------------------- 1 | module fun_with_algorithms_and_data_structures 2 | 3 | go 1.20 4 | 5 | require golang.org/x/exp v0.0.0-20230713183714-613f0c0eb8a1 6 | -------------------------------------------------------------------------------- /go.sum: -------------------------------------------------------------------------------- 1 | golang.org/x/exp v0.0.0-20230713183714-613f0c0eb8a1 h1:MGwJjxBy0HJshjDNfLsYO8xppfqWlA5ZT9OhtUUhTNw= 2 | golang.org/x/exp v0.0.0-20230713183714-613f0c0eb8a1/go.mod h1:FXUEEKJgO7OQYeo8N01OfiKP8RXMtf6e8aTskBGqWdc= 3 | -------------------------------------------------------------------------------- /node_chain/node_chain.go: -------------------------------------------------------------------------------- 1 | package node_chain 2 | 3 | import ( 4 | "fmt" 5 | "strings" 6 | ) 7 | 8 | type Node[T any] struct { 9 | Value T 10 | Next *Node[T] 11 | } 12 | 13 | func (n *Node[value]) String() string { 14 | var sb strings.Builder 15 | fmt.Fprintf(&sb, "%v", n.Value) 16 | 17 | curr := n 18 | for curr.Next != nil { 19 | curr = curr.Next 20 | fmt.Fprintf(&sb, " %v", curr.Value) 21 | } 22 | 23 | return sb.String() 24 | } 25 | -------------------------------------------------------------------------------- /linked_list/enumerator.go: -------------------------------------------------------------------------------- 1 | package linked_list 2 | 3 | type Enumerator[T any] struct { 4 | Current *Node[T] 5 | List *LinkedList[T] 6 | } 7 | 8 | func (e *Enumerator[T]) getNext() *Node[T] { 9 | if e.Current == nil { 10 | e.Current = e.List.Head 11 | } else { 12 | temp := e.Current.Next 13 | e.Current = temp 14 | } 15 | return e.Current 16 | } 17 | 18 | func (l *LinkedList[T]) enumerator() Enumerator[T] { 19 | return Enumerator[T]{ 20 | List: l, 21 | } 22 | } 23 | -------------------------------------------------------------------------------- /.gitignore: -------------------------------------------------------------------------------- 1 | # If you prefer the allow list template instead of the deny list, see community template: 2 | # https://github.com/github/gitignore/blob/main/community/Golang/Go.AllowList.gitignore 3 | # 4 | # Binaries for programs and plugins 5 | *.exe 6 | *.exe~ 7 | *.dll 8 | *.so 9 | *.dylib 10 | 11 | # Test binary, built with `go test -c` 12 | *.test 13 | 14 | # Output of the go coverage tool, specifically when used with LiteIDE 15 | *.out 16 | 17 | # Dependency directories (remove the comment below to include it) 18 | # vendor/ 19 | 20 | # Go workspace file 21 | go.work 22 | -------------------------------------------------------------------------------- /avl_tree/avl_tree_test.go: -------------------------------------------------------------------------------- 1 | package avl_tree 2 | 3 | import ( 4 | "testing" 5 | ) 6 | 7 | func TestRandomDataIsInOrder(t *testing.T) { 8 | tree := NewAVLTree[int]() 9 | 10 | tree.Add(98) 11 | tree.Add(22) 12 | tree.Add(14) 13 | tree.Add(72) 14 | tree.Add(44) 15 | tree.Add(25) 16 | tree.Add(63) 17 | 18 | want := []int{14, 22, 25, 44, 63, 72, 98} // ordered slice 19 | got := tree.InOrder() 20 | 21 | if len(got) != len(want) { 22 | t.Errorf("got slice of size %d, want size %d ", len(got), len(want)) 23 | } else { 24 | for i, v := range got { 25 | if want[i] != got[i] { 26 | t.Errorf("value at %d: want %d, got %d ", i, want[i], v) 27 | } 28 | } 29 | } 30 | } 31 | -------------------------------------------------------------------------------- /graph/graph_test.go: -------------------------------------------------------------------------------- 1 | package graph 2 | 3 | import ( 4 | "testing" 5 | ) 6 | 7 | func TestTraverseGraph(t *testing.T) { 8 | 9 | nodeA := NewNode("A") 10 | nodeB := NewNode("B") 11 | nodeC := NewNode("C") 12 | nodeD := NewNode("D") 13 | nodeE := NewNode("E") 14 | nodeF := NewNode("F") 15 | nodeG := NewNode("G") 16 | 17 | nodeA.AddEdge(&nodeB, 3) 18 | nodeA.AddEdge(&nodeC, 3) 19 | 20 | nodeB.AddEdge(&nodeC, 6) 21 | nodeB.AddEdge(&nodeD, 5) 22 | 23 | nodeC.AddEdge(&nodeD, 11) 24 | nodeC.AddEdge(&nodeE, 8) 25 | 26 | nodeD.AddEdge(&nodeE, 2) 27 | nodeD.AddEdge(&nodeF, 10) 28 | nodeD.AddEdge(&nodeG, 2) 29 | 30 | nodeE.AddEdge(&nodeG, 5) 31 | nodeF.AddEdge(&nodeG, 3) 32 | 33 | labels := BreadthFirst[string](&nodeA) 34 | numEdges := 12 35 | 36 | if len(labels) != numEdges { 37 | t.Errorf("want %d labels from %d edges, got %d", numEdges, numEdges, len(labels)) 38 | } 39 | } 40 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # Fun With Algorithms and Data Structures in Go 2 | 3 | _"Algorithms + Data Structures = Programs" - Niklaus Wirth_ 4 | 5 | NB: This code isn't at all production ready. It's intended for educational purposes only. 6 | 7 | ## Data Structures 8 | * [Node Chain](node_chain/node_chain.go) 9 | * [Linked List](linked_list/linked_list.go) 10 | * [Stack](stack/stack.go) 11 | * [Queue](queue/queue.go) 12 | * [Binary Tree](binary_tree/binary_tree.go) 13 | * [AVL Tree](avl_tree/avl_tree.go) 14 | * [Heap](heap/heap.go) 15 | * [Graph](graph/graph.go) 16 | 17 | ## Algorithms 18 | * [Sorting](sort/sort.go) 19 | * [Bubble Sort](sort/sort.go#L5) 20 | * [Insertion Sort](sort/sort.go#L19) 21 | * [Selection Sort](sort/sort.go#L35) 22 | * [Merge Sort](sort/sort.go#L82) 23 | * [Quick Sort](sort/sort.go#L92) 24 | * [Dijkstra's shortest path](dijkstra/dijkstra.go) 25 | 26 | ## Run Tests 27 | 28 | ``` 29 | go test -v ./... 30 | ``` 31 | -------------------------------------------------------------------------------- /node_chain/node_chain_test.go: -------------------------------------------------------------------------------- 1 | package node_chain 2 | 3 | import ( 4 | "fmt" 5 | "testing" 6 | ) 7 | 8 | type nv int // so we can add a String() func 9 | 10 | func (n nv) String() string { 11 | return fmt.Sprintf("%d", n) 12 | } 13 | 14 | func TestNodeChain(t *testing.T) { 15 | tail := Node[nv]{Value: 3} 16 | body := Node[nv]{Value: 2, Next: &tail} 17 | head := Node[nv]{Value: 1, Next: &body} 18 | 19 | want := "1 2 3" 20 | got := head.String() 21 | if want != got { 22 | t.Errorf("got %s, want %s", got, want) 23 | } 24 | } 25 | 26 | func TestMove(t *testing.T) { 27 | 28 | tail := Node[nv]{Value: 4} 29 | second := Node[nv]{Value: 3, Next: &tail} 30 | first := Node[nv]{Value: 2, Next: &second} 31 | head := Node[nv]{Value: 1, Next: &first} 32 | 33 | first.Next = &tail 34 | second.Next = &first 35 | head.Next = &second 36 | 37 | want := "1 3 2 4" 38 | got := head.String() 39 | if want != got { 40 | t.Errorf("got %s, want %s", got, want) 41 | } 42 | } 43 | -------------------------------------------------------------------------------- /queue/queue.go: -------------------------------------------------------------------------------- 1 | package queue 2 | 3 | import ( 4 | "fmt" 5 | "fun_with_algorithms_and_data_structures/linked_list" 6 | "strings" 7 | ) 8 | 9 | type Queue[T any] struct { 10 | linkedList linked_list.LinkedList[T] 11 | } 12 | 13 | func new[T any]() Queue[T] { 14 | st := Queue[T]{} 15 | st.linkedList = linked_list.LinkedList[T]{} 16 | return st 17 | } 18 | 19 | func (q *Queue[T]) Enqueue(o T) { 20 | node := linked_list.Node[T]{} 21 | node.Value = o 22 | q.linkedList.AddTail(&node) 23 | } 24 | 25 | func (q *Queue[T]) Dequeue() error { 26 | if q.linkedList.Count == 0 { 27 | return fmt.Errorf("error: cannot dequeue from an empty queue") 28 | } 29 | q.linkedList.RemoveHead() 30 | 31 | return nil 32 | } 33 | 34 | func (q *Queue[T]) Peek() (T, error) { 35 | var r T 36 | if q.linkedList.Count == 0 { 37 | return r, fmt.Errorf("error: cannot peek an empty queue") 38 | } 39 | 40 | r = q.linkedList.Head.Value 41 | return r, nil 42 | } 43 | 44 | func (q *Queue[T]) String() string { 45 | var sb strings.Builder 46 | fmt.Fprint(&sb, "START") 47 | 48 | node := q.linkedList.Head 49 | for node != nil { 50 | fmt.Fprintf(&sb, " %v", node.Value) 51 | node = node.Next 52 | } 53 | 54 | fmt.Fprint(&sb, " END") 55 | return sb.String() 56 | } 57 | -------------------------------------------------------------------------------- /dijkstra/priority_queue.go: -------------------------------------------------------------------------------- 1 | package dijkstra 2 | 3 | import "sort" 4 | 5 | type PriorityQueue struct { 6 | keys []string 7 | nodes map[string]int 8 | } 9 | 10 | func NewQueue() *PriorityQueue { 11 | var q PriorityQueue 12 | q.nodes = make(map[string]int) 13 | return &q 14 | } 15 | 16 | func (q *PriorityQueue) Len() int { 17 | return len(q.keys) 18 | } 19 | 20 | func (q *PriorityQueue) Swap(i, j int) { 21 | q.keys[i], q.keys[j] = q.keys[j], q.keys[i] 22 | } 23 | 24 | func (q *PriorityQueue) Less(i, j int) bool { 25 | a := q.keys[i] 26 | b := q.keys[j] 27 | 28 | return q.nodes[a] < q.nodes[b] 29 | } 30 | 31 | func (q *PriorityQueue) Update(node Node) { 32 | if _, ok := q.nodes[node.Value]; !ok { 33 | q.keys = append(q.keys, node.Value) 34 | } 35 | 36 | q.nodes[node.Value] = node.Distance 37 | 38 | sort.Sort(q) 39 | } 40 | 41 | func (q *PriorityQueue) Next() Node { 42 | val, keys := q.keys[0], q.keys[1:] 43 | q.keys = keys 44 | 45 | dist := q.nodes[val] 46 | delete(q.nodes, val) 47 | 48 | return Node{val, dist} 49 | } 50 | 51 | func (q *PriorityQueue) Empty() bool { 52 | return len(q.keys) == 0 53 | } 54 | 55 | func (q *PriorityQueue) Peek(val string) (priority int, ok bool) { 56 | priority, ok = q.nodes[val] 57 | return 58 | } 59 | -------------------------------------------------------------------------------- /stack/stack.go: -------------------------------------------------------------------------------- 1 | package stack 2 | 3 | import ( 4 | "fmt" 5 | "fun_with_algorithms_and_data_structures/linked_list" 6 | "strings" 7 | ) 8 | 9 | type Stack[T any] struct { 10 | linkedList linked_list.LinkedList[T] 11 | } 12 | 13 | func new[T any]() Stack[T] { 14 | st := Stack[T]{} 15 | st.linkedList = linked_list.LinkedList[T]{} 16 | return st 17 | } 18 | 19 | func (s *Stack[T]) Push(o T) { 20 | node := linked_list.Node[T]{} 21 | node.Value = o 22 | s.linkedList.AddHead(&node) 23 | } 24 | 25 | func (s *Stack[T]) Peek() (T, error) { 26 | var r T 27 | if s.linkedList.Count == 0 { 28 | return r, fmt.Errorf("error: cannot peek an empty stack") 29 | } 30 | return s.linkedList.Head.Value, nil 31 | } 32 | 33 | func (s *Stack[T]) Pop() (T, error) { 34 | var r T 35 | if s.linkedList.Count == 0 { 36 | return r, fmt.Errorf("error: cannot pop from empty stack") 37 | } 38 | r, err := s.Peek() 39 | if err != nil { 40 | return r, err 41 | } 42 | s.linkedList.RemoveHead() 43 | 44 | return r, nil 45 | } 46 | 47 | func (s *Stack[T]) String() string { 48 | var sb strings.Builder 49 | fmt.Fprint(&sb, "TOP") 50 | 51 | node := s.linkedList.Head 52 | for node != nil { 53 | fmt.Fprintf(&sb, "\n%v", node.Value) 54 | node = node.Next 55 | } 56 | return sb.String() 57 | } 58 | -------------------------------------------------------------------------------- /dijkstra/dijkstra.go: -------------------------------------------------------------------------------- 1 | package dijkstra 2 | 3 | type Node struct { 4 | Value string 5 | Distance int 6 | } 7 | 8 | type Edge map[string]int 9 | 10 | type Graph map[string]Edge 11 | 12 | func (g Graph) ShortestPath(from, to string) ([]string, int) { 13 | var path []string 14 | var distance int 15 | 16 | visited := make(map[string]bool) 17 | prev := make(map[string]string) 18 | 19 | q := NewQueue() 20 | 21 | q.Update(Node{from, 0}) 22 | 23 | for !q.Empty() { 24 | n := q.Next() 25 | 26 | if n.Value == to { 27 | distance = n.Distance 28 | 29 | nVal := n.Value 30 | for nVal != from { 31 | path = append(path, nVal) 32 | nVal = prev[nVal] 33 | } 34 | 35 | break 36 | } 37 | 38 | visited[n.Value] = true 39 | 40 | for nVal, nDist := range g[n.Value] { 41 | if visited[nVal] { 42 | continue 43 | } 44 | 45 | if _, ok := q.Peek(nVal); !ok { 46 | prev[nVal] = n.Value 47 | q.Update(Node{nVal, n.Distance + nDist}) 48 | continue 49 | } 50 | 51 | routeLen, _ := q.Peek(nVal) 52 | nodeLen := n.Distance + nDist 53 | 54 | if nodeLen < routeLen { 55 | prev[nVal] = n.Value 56 | q.Update(Node{nVal, nodeLen}) 57 | } 58 | } 59 | } 60 | 61 | path = append(path, from) 62 | flip(path) 63 | 64 | return path, distance 65 | } 66 | 67 | func flip(path []string) { 68 | for i, j := 0, len(path)-1; i < j; i, j = i+1, j-1 { 69 | path[i], path[j] = path[j], path[i] 70 | } 71 | } 72 | -------------------------------------------------------------------------------- /queue/queue_test.go: -------------------------------------------------------------------------------- 1 | package queue 2 | 3 | import "testing" 4 | 5 | func TestEmptyQueue(t *testing.T) { 6 | queue := new[string]() 7 | got := queue.String() 8 | want := "START END" 9 | 10 | if got != want { 11 | t.Errorf("got %s, want %s", got, want) 12 | } 13 | } 14 | 15 | func TestEnqueue(t *testing.T) { 16 | queue := new[string]() 17 | queue.Enqueue("MIDDLE") 18 | 19 | got := queue.String() 20 | want := "START MIDDLE END" 21 | 22 | if got != want { 23 | t.Errorf("got %s, want %s", got, want) 24 | } 25 | } 26 | 27 | func TestDequeue(t *testing.T) { 28 | queue := new[string]() 29 | queue.Enqueue("ONE") 30 | queue.Enqueue("TWO") 31 | queue.Enqueue("THREE") 32 | 33 | queue.Dequeue() 34 | 35 | got := queue.String() 36 | want := "START TWO THREE END" 37 | 38 | if got != want { 39 | t.Errorf("got %s, want %s", got, want) 40 | } 41 | } 42 | 43 | func TestDequeueEmptyQueue(t *testing.T) { 44 | queue := new[string]() 45 | 46 | err := queue.Dequeue() 47 | if err == nil { 48 | t.Error("error: no error dequeuing from empty queue") 49 | } 50 | } 51 | 52 | func TestPeek(t *testing.T) { 53 | queue := new[string]() 54 | want := "ONE" 55 | queue.Enqueue(want) 56 | 57 | got, _ := queue.Peek() 58 | if got != want { 59 | t.Errorf("got %s, want %s", got, want) 60 | } 61 | } 62 | 63 | func TestPeekEmptyQueue(t *testing.T) { 64 | queue := new[string]() 65 | 66 | _, err := queue.Peek() 67 | if err == nil { 68 | t.Error("error: no error peeking empty queue") 69 | } 70 | } 71 | -------------------------------------------------------------------------------- /graph/graph.go: -------------------------------------------------------------------------------- 1 | package graph 2 | 3 | // Node (AKA a Vertex) contains a slice of edges which is all 4 | // of its connections to other nodes. 5 | type Node[T comparable] struct { 6 | Value T 7 | Edges []*Edge[T] 8 | } 9 | 10 | func NewNode[T comparable](val T) Node[T] { 11 | return Node[T]{Value: val} 12 | } 13 | 14 | func (n *Node[T]) AddEdge(to *Node[T], weight int) { 15 | n.Edges = append(n.Edges, &Edge[T]{ToNode: to, Weight: weight}) 16 | } 17 | 18 | // Edge represents a link between nodes. This is a directed graph 19 | // so an edge just has a node it is connected to. 20 | type Edge[T comparable] struct { 21 | ToNode *Node[T] 22 | Weight int 23 | visited bool 24 | } 25 | 26 | // unvisited returns all of the edges that haven't been traversed yet 27 | func unvisited[T comparable](edges []*Edge[T]) []*Node[T] { 28 | unv := []*Node[T]{} 29 | for _, edge := range edges { 30 | if !edge.visited { 31 | unv = append(unv, edge.ToNode) 32 | edge.visited = true 33 | } 34 | } 35 | return unv 36 | } 37 | 38 | // trvse recursively walks through the entire graph 39 | func bfs[T comparable](node *Node[T], vals *[]T) { 40 | if node != nil { 41 | *vals = append(*vals, node.Value) 42 | for _, n := range unvisited(node.Edges) { 43 | bfs(n, vals) 44 | } 45 | } 46 | } 47 | 48 | // BreadthFirst traverses through the directed graph visiting nodes 49 | // until it has traveled via all edges. 50 | func BreadthFirst[T comparable](start *Node[T]) []T { 51 | vals := []T{} 52 | bfs(start, &vals) 53 | return vals 54 | } 55 | -------------------------------------------------------------------------------- /dijkstra/dijkstra_test.go: -------------------------------------------------------------------------------- 1 | package dijkstra 2 | 3 | import ( 4 | "testing" 5 | ) 6 | 7 | func TestShortestPath(t *testing.T) { 8 | 9 | graph := Graph{ 10 | "London": {"Birmingham": 202, "Bristol": 190, "Salford": 333}, 11 | "Birmingham": {"London": 202, "Bristol": 142}, 12 | "Bristol": {"Cardiff": 45, "London": 190, "Birmingham": 142}, 13 | "Cardiff": {"Bristol": 45}, 14 | "Salford": {"Glasgow": 340, "Birmingham": 151}, 15 | "Glasgow": {"Salford": 340}, 16 | } 17 | 18 | gotPath, _ := graph.ShortestPath("Cardiff", "Glasgow") 19 | wantPath := []string{"Cardiff", "Bristol", "London", "Salford", "Glasgow"} 20 | 21 | if len(gotPath) != len(wantPath) { 22 | t.Errorf("wanted path %v, got %v", wantPath, gotPath) 23 | } 24 | 25 | for i, v := range gotPath { 26 | if wantPath[i] != gotPath[i] { 27 | t.Errorf("value at %d: want %s, got %s ", i, wantPath[i], v) 28 | } 29 | } 30 | } 31 | 32 | func TestDistance(t *testing.T) { 33 | 34 | graph := Graph{ 35 | "London": {"Birmingham": 202, "Bristol": 190, "Salford": 333}, 36 | "Birmingham": {"London": 202, "Bristol": 142}, 37 | "Bristol": {"Cardiff": 45, "London": 190, "Birmingham": 142}, 38 | "Cardiff": {"Bristol": 45}, 39 | "Salford": {"Glasgow": 340, "Birmingham": 151}, 40 | "Glasgow": {"Salford": 340}, 41 | } 42 | 43 | _, gotDistance := graph.ShortestPath("Cardiff", "Glasgow") 44 | 45 | wantDistance := 908 46 | if gotDistance != wantDistance { 47 | t.Errorf("wanted distance %d, got %d", wantDistance, gotDistance) 48 | } 49 | 50 | } 51 | -------------------------------------------------------------------------------- /heap/heap.go: -------------------------------------------------------------------------------- 1 | package heap 2 | 3 | type Heap[T any] struct { 4 | Data []T 5 | } 6 | 7 | func NewHeap[T any]() *Heap[T] { 8 | return &Heap[T]{ 9 | Data: make([]T, 0), 10 | } 11 | } 12 | 13 | func (h *Heap[T]) Insert(f func(T, T) bool, v T) { 14 | h.Data = append(h.Data, v) 15 | h.siftUp(f, (len(h.Data) - 1)) 16 | } 17 | 18 | func (h *Heap[T]) Extract(f func(T, T) bool) (T, bool) { 19 | var val T 20 | if h.Size() == 0 { 21 | return val, false 22 | } 23 | val = h.Data[0] 24 | h.swap(0, h.Size()-1) 25 | h.Data = h.Data[:h.Size()-1] 26 | h.siftDown(f, 0) 27 | 28 | return val, true 29 | } 30 | 31 | func (h *Heap[T]) Size() int { 32 | return len(h.Data) 33 | } 34 | 35 | func (h *Heap[T]) siftUp(f func(T, T) bool, i int) { 36 | 37 | for f(h.Data[parentIndex(i)], h.Data[i]) { 38 | h.swap(i, parentIndex(i)) 39 | i = parentIndex(i) 40 | } 41 | } 42 | 43 | func (h *Heap[T]) siftDown(f func(T, T) bool, i int) { 44 | l, r, largest := leftChildIndex(i), rightChildIndex(i), i 45 | 46 | if l < len(h.Data) && f(h.Data[i], h.Data[l]) { 47 | largest = l 48 | } 49 | 50 | if r < len(h.Data) && f(h.Data[largest], h.Data[r]) { 51 | largest = r 52 | } 53 | 54 | if largest != i { 55 | h.swap(i, largest) 56 | h.siftDown(f, largest) 57 | } 58 | } 59 | 60 | func (h *Heap[T]) swap(i, j int) { 61 | h.Data[i], h.Data[j] = h.Data[j], h.Data[i] 62 | } 63 | 64 | func leftChildIndex(i int) int { 65 | return 2*i + 1 66 | } 67 | 68 | func rightChildIndex(i int) int { 69 | return 2*i + 2 70 | } 71 | 72 | func parentIndex(i int) int { 73 | return (i - 1) / 2 74 | } 75 | -------------------------------------------------------------------------------- /linked_list/linked_list.go: -------------------------------------------------------------------------------- 1 | package linked_list 2 | 3 | import ( 4 | "fmt" 5 | "strings" 6 | ) 7 | 8 | type Node[T any] struct { 9 | Value T 10 | Next *Node[T] 11 | } 12 | 13 | type LinkedList[T any] struct { 14 | Head *Node[T] 15 | Tail *Node[T] 16 | Count int 17 | } 18 | 19 | // AddHead adds a node to the head of the list. 20 | func (l *LinkedList[T]) AddHead(n *Node[T]) { 21 | temp := l.Head 22 | l.Head = n 23 | l.Head.Next = temp 24 | l.Count++ 25 | if l.Count == 1 { 26 | l.Tail = l.Head 27 | } 28 | } 29 | 30 | // AddTail adds a node to the tail of the list. 31 | func (l *LinkedList[T]) AddTail(n *Node[T]) { 32 | if l.Count == 0 { 33 | l.Head = n 34 | l.Tail = n 35 | } else { 36 | l.Tail.Next = n 37 | } 38 | 39 | l.Tail = n 40 | 41 | l.Count++ 42 | } 43 | 44 | // RemoveHead removes a node from the head of the list. 45 | func (l *LinkedList[T]) RemoveHead() { 46 | if l.Count != 0 { 47 | l.Head = l.Head.Next 48 | l.Count-- 49 | if l.Count == 0 { 50 | l.Tail = nil 51 | } 52 | } 53 | 54 | } 55 | 56 | // RemoveTail removes a node from the tail of the list. 57 | // Loops through entire list so decreases in performance by O(n) 58 | func (l *LinkedList[T]) RemoveTail() { 59 | if l.Count != 0 { 60 | if l.Count == 1 { 61 | l.Head = nil 62 | l.Tail = nil 63 | } else { 64 | current := l.Head 65 | for current.Next != l.Tail { 66 | current = current.Next 67 | } 68 | current.Next = nil 69 | l.Tail = current 70 | } 71 | l.Count-- 72 | } 73 | 74 | } 75 | 76 | func (l *LinkedList[T]) String() string { 77 | var sb strings.Builder 78 | fmt.Fprint(&sb, "HEAD") 79 | 80 | node := l.Head 81 | for node != nil { 82 | fmt.Fprintf(&sb, "->%v", node.Value) 83 | node = node.Next 84 | } 85 | 86 | fmt.Fprint(&sb, "->TAIL") 87 | return sb.String() 88 | } 89 | -------------------------------------------------------------------------------- /stack/stack_test.go: -------------------------------------------------------------------------------- 1 | package stack 2 | 3 | import "testing" 4 | 5 | func TestEmptyStack(t *testing.T) { 6 | stack := new[string]() 7 | got := stack.String() 8 | want := "TOP" 9 | 10 | if got != want { 11 | t.Errorf("got %s, want %s", got, want) 12 | } 13 | } 14 | 15 | func TestPush(t *testing.T) { 16 | stack := new[string]() 17 | stack.Push("ONE") 18 | stack.Push("TWO") 19 | 20 | want := "TOP\nTWO\nONE" 21 | got := stack.String() 22 | 23 | if got != want { 24 | t.Errorf("got %s, want %s", got, want) 25 | } 26 | 27 | } 28 | 29 | func TestPeek(t *testing.T) { 30 | stack := new[string]() 31 | stack.Push("ONE") 32 | stack.Push("TWO") 33 | 34 | itemGot, _ := stack.Peek() 35 | itemWant := "TWO" 36 | 37 | if itemGot != itemWant { 38 | t.Errorf("got item %s, want item %s", itemGot, itemWant) 39 | } 40 | 41 | wantStack := "TOP\nTWO\nONE" 42 | gotStack := stack.String() 43 | 44 | if gotStack != wantStack { 45 | t.Errorf("got %s, want %s", gotStack, wantStack) 46 | } 47 | } 48 | 49 | func TestPeekFromEmpty(t *testing.T) { 50 | stack := new[string]() 51 | 52 | _, err := stack.Peek() 53 | if err == nil { 54 | t.Errorf("pop from empty stack should be error") 55 | } 56 | } 57 | 58 | func TestPop(t *testing.T) { 59 | stack := new[string]() 60 | stack.Push("ONE") 61 | stack.Push("TWO") 62 | 63 | itemGot, _ := stack.Pop() 64 | itemWant := "TWO" 65 | 66 | if itemGot != itemWant { 67 | t.Errorf("got item %s, want item %s", itemGot, itemWant) 68 | } 69 | 70 | wantStack := "TOP\nONE" 71 | gotStack := stack.String() 72 | 73 | if gotStack != wantStack { 74 | t.Errorf("got %s, want %s", gotStack, wantStack) 75 | } 76 | } 77 | 78 | func TestPopFromEmpty(t *testing.T) { 79 | stack := new[string]() 80 | 81 | _, err := stack.Pop() 82 | if err == nil { 83 | t.Errorf("pop from empty stack should be error") 84 | } 85 | } 86 | -------------------------------------------------------------------------------- /sort/sort_test.go: -------------------------------------------------------------------------------- 1 | package sort 2 | 3 | import ( 4 | "testing" 5 | ) 6 | 7 | func TestBubbleSort(t *testing.T) { 8 | 9 | items := []int{17, 3, 15, 14, 18, 4, 8, 53, 2, 16, 10, 5, 20, 100, 1, 12, 21, 13, 9, 19, 7, 11, 6} 10 | BubbleSort[int](items) 11 | lower := 0 12 | 13 | for _, item := range items { 14 | if item < lower { 15 | t.Errorf("item %d found before %d", item, lower) 16 | } 17 | lower = item 18 | } 19 | } 20 | 21 | func TestInsertionSort(t *testing.T) { 22 | items := []int{17, 3, 15, 14, 18, 4, 8, 53, 2, 16, 10, 5, 20, 100, 1, 12, 21, 13, 9, 19, 7, 11, 6} 23 | InsertionSort[int](items) 24 | lower := 0 25 | 26 | for _, item := range items { 27 | if item < lower { 28 | t.Errorf("item %d found before %d", item, lower) 29 | } 30 | lower = item 31 | } 32 | } 33 | 34 | func TestSelectionSort(t *testing.T) { 35 | items := []int{17, 3, 15, 14, 18, 4, 8, 53, 2, 16, 10, 5, 20, 100, 1, 12, 21, 13, 9, 19, 7, 11, 6} 36 | SelectionSort[int](items) 37 | lower := 0 38 | 39 | for _, item := range items { 40 | if item < lower { 41 | t.Errorf("item %d found before %d", item, lower) 42 | } 43 | lower = item 44 | } 45 | } 46 | 47 | func TestMergeSort(t *testing.T) { 48 | items := []int{17, 3, 15, 14, 18, 4, 8, 53, 2, 16, 10, 5, 20, 100, 1, 12, 21, 13, 9, 19, 7, 11, 6} 49 | got := MergeSort[int](items) 50 | lower := 0 51 | 52 | for _, item := range got { 53 | if item < lower { 54 | t.Errorf("item %d found before %d", item, lower) 55 | } 56 | lower = item 57 | } 58 | } 59 | 60 | func TestQuickSort(t *testing.T) { 61 | items := []int{17, 3, 15, 14, 18, 4, 8, 53, 2, 16, 10, 5, 20, 100, 1, 12, 21, 13, 9, 19, 7, 11, 6} 62 | QuickSort[int](items) 63 | lower := 0 64 | 65 | for _, item := range items { 66 | if item < lower { 67 | t.Errorf("item %d found before %d", item, lower) 68 | } 69 | lower = item 70 | } 71 | } 72 | -------------------------------------------------------------------------------- /sort/sort.go: -------------------------------------------------------------------------------- 1 | package sort 2 | 3 | import "golang.org/x/exp/constraints" 4 | 5 | func BubbleSort[T constraints.Ordered](items []T) { 6 | if len(items) < 2 { 7 | return 8 | } 9 | 10 | for i := len(items); i > 0; i-- { 11 | for j := 1; j < i; j++ { 12 | if items[j-1] > items[j] { 13 | items[j-1], items[j] = items[j], items[j-1] 14 | } 15 | } 16 | } 17 | } 18 | 19 | func InsertionSort[T constraints.Ordered](items []T) { 20 | if len(items) < 2 { 21 | return 22 | } 23 | 24 | for i := 1; i < len(items); i++ { 25 | j := i 26 | for j > 0 { 27 | if items[j-1] > items[j] { 28 | items[j-1], items[j] = items[j], items[j-1] 29 | } 30 | j-- 31 | } 32 | } 33 | } 34 | 35 | func SelectionSort[T constraints.Ordered](items []T) { 36 | if len(items) < 2 { 37 | return 38 | } 39 | 40 | var m int 41 | 42 | for i := 0; i < len(items)-1; i++ { 43 | m = i 44 | 45 | for j := i + 1; j < len(items); j++ { 46 | if items[j] < items[m] { 47 | m = j 48 | } 49 | } 50 | items[m], items[i] = items[i], items[m] 51 | } 52 | 53 | } 54 | 55 | func merge[T constraints.Ordered](left []T, right []T) []T { 56 | 57 | var i, j int 58 | size := len(left) + len(right) 59 | m := make([]T, size) 60 | 61 | for k := 0; k < size; k++ { 62 | if i > len(left)-1 && j <= len(right)-1 { 63 | m[k] = right[j] 64 | j++ 65 | 66 | } else if j > len(right)-1 && i <= len(left)-1 { 67 | m[k] = left[i] 68 | i++ 69 | 70 | } else if left[i] < right[j] { 71 | m[k] = left[i] 72 | 73 | } else { 74 | m[k] = right[j] 75 | j++ 76 | } 77 | } 78 | 79 | return m 80 | } 81 | 82 | func MergeSort[T constraints.Ordered](items []T) []T { 83 | if len(items) < 2 { 84 | return items 85 | } 86 | 87 | mid := (len(items)) / 2 88 | 89 | return merge(MergeSort(items[:mid]), MergeSort(items[mid:])) 90 | } 91 | 92 | func QuickSort[T constraints.Ordered](items []T) { 93 | quickSort(items, 0, len(items)-1) 94 | } 95 | 96 | func quickSort[T constraints.Ordered](items []T, start int, end int) { 97 | if start < end { 98 | pi := partition(items, start, end) 99 | quickSort(items, start, pi-1) 100 | quickSort(items, pi+1, end) 101 | } 102 | } 103 | 104 | func partition[T constraints.Ordered](items []T, start, end int) int { 105 | pivot := items[end] 106 | i := start - 1 107 | 108 | for j := start; j < end; j++ { 109 | if items[j] <= pivot { 110 | i++ 111 | items[i], items[j] = items[j], items[i] 112 | } 113 | } 114 | 115 | items[i+1], items[end] = items[end], items[i+1] 116 | 117 | return i + 1 118 | } 119 | -------------------------------------------------------------------------------- /heap/heap_test.go: -------------------------------------------------------------------------------- 1 | package heap 2 | 3 | import ( 4 | "testing" 5 | 6 | "golang.org/x/exp/constraints" 7 | ) 8 | 9 | func max[T constraints.Ordered](a, b T) bool { 10 | return a < b 11 | } 12 | 13 | func min[T constraints.Ordered](a, b T) bool { 14 | return a > b 15 | } 16 | 17 | func TestMaxHeapExtract(t *testing.T) { 18 | 19 | heap := NewHeap[int]() 20 | want := 99 21 | 22 | heap.Insert(max[int], 72) 23 | heap.Insert(max[int], 22) 24 | heap.Insert(max[int], want) 25 | 26 | got, ok := heap.Extract(max[int]) 27 | 28 | if !ok { 29 | t.Errorf("error extracting item from heap") 30 | } else { 31 | if got != want { 32 | t.Errorf("extract: want %d, got %d", want, got) 33 | } 34 | } 35 | } 36 | 37 | func TestMinHeapExtract(t *testing.T) { 38 | 39 | heap := NewHeap[int]() 40 | want := 22 41 | 42 | heap.Insert(min[int], 72) 43 | heap.Insert(min[int], 99) 44 | heap.Insert(min[int], want) 45 | 46 | got, ok := heap.Extract(max[int]) 47 | 48 | if !ok { 49 | t.Errorf("error extracting item from heap") 50 | } else { 51 | if got != want { 52 | t.Errorf("extract: want %d, got %d", want, got) 53 | } 54 | } 55 | } 56 | 57 | func TestMaxHeapPriority(t *testing.T) { 58 | 59 | heap := NewHeap[int]() 60 | items := []int{72, 22, 12, 7, 89, 44} 61 | 62 | for _, n := range items { 63 | heap.Insert(max[int], n) 64 | } 65 | 66 | got := []int{} 67 | for range items { // use size of items 68 | item, ok := heap.Extract(max[int]) 69 | if ok { 70 | got = append(got, item) 71 | } 72 | } 73 | 74 | if got == nil { 75 | t.Error("returned nil values") 76 | } 77 | 78 | // highest priority is the highest number for this example 79 | want := []int{89, 72, 44, 22, 12, 7} 80 | for i, v := range got { 81 | if want[i] != got[i] { 82 | t.Errorf("value at %d: want %d, got %d ", i, want[i], v) 83 | } 84 | } 85 | } 86 | 87 | func TestMinHeapPriority(t *testing.T) { 88 | 89 | heap := NewHeap[int]() 90 | items := []int{72, 22, 12, 7, 89, 44} 91 | 92 | for _, n := range items { 93 | heap.Insert(min[int], n) 94 | } 95 | 96 | got := []int{} 97 | for range items { // use size of items 98 | item, ok := heap.Extract(min[int]) 99 | if ok { 100 | got = append(got, item) 101 | } 102 | } 103 | 104 | if got == nil { 105 | t.Error("returned nil values") 106 | } 107 | 108 | // lowest priority is the highest number for this example 109 | want := []int{7, 12, 22, 44, 72, 89} 110 | for i, v := range got { 111 | if want[i] != got[i] { 112 | t.Errorf("value at %d: want %d, got %d ", i, want[i], v) 113 | } 114 | } 115 | } 116 | -------------------------------------------------------------------------------- /linked_list/linked_list_test.go: -------------------------------------------------------------------------------- 1 | package linked_list 2 | 3 | import "testing" 4 | 5 | func TestEmptyLinkedList(t *testing.T) { 6 | 7 | var ll LinkedList[string] 8 | 9 | want := "HEAD->TAIL" 10 | got := ll.String() 11 | 12 | if got != want { 13 | t.Errorf("got %s, want %s", got, want) 14 | } 15 | 16 | } 17 | 18 | func TestAddToHead(t *testing.T) { 19 | 20 | var ll LinkedList[string] 21 | 22 | ll.AddHead(&Node[string]{Value: "ONE"}) 23 | 24 | want := "HEAD->ONE->TAIL" 25 | got := ll.String() 26 | 27 | if got != want { 28 | t.Errorf("got %s, want %s", got, want) 29 | } 30 | 31 | } 32 | 33 | func TestAddMultipleToHead(t *testing.T) { 34 | 35 | var ll LinkedList[string] 36 | 37 | ll.AddHead(&Node[string]{Value: "THREE"}) 38 | ll.AddHead(&Node[string]{Value: "TWO"}) 39 | ll.AddHead(&Node[string]{Value: "ONE"}) 40 | 41 | want := "HEAD->ONE->TWO->THREE->TAIL" 42 | got := ll.String() 43 | 44 | if got != want { 45 | t.Errorf("got %s, want %s", got, want) 46 | } 47 | 48 | } 49 | 50 | func TestAddToTail(t *testing.T) { 51 | var ll LinkedList[string] 52 | 53 | ll.AddTail(&Node[string]{Value: "ONE"}) 54 | 55 | want := "HEAD->ONE->TAIL" 56 | got := ll.String() 57 | 58 | if got != want { 59 | t.Errorf("got %s, want %s", got, want) 60 | } 61 | } 62 | 63 | func TestMultipleAddToTail(t *testing.T) { 64 | var ll LinkedList[string] 65 | 66 | ll.AddTail(&Node[string]{Value: "ONE"}) 67 | ll.AddTail(&Node[string]{Value: "TWO"}) 68 | ll.AddTail(&Node[string]{Value: "THREE"}) 69 | 70 | want := "HEAD->ONE->TWO->THREE->TAIL" 71 | got := ll.String() 72 | 73 | if got != want { 74 | t.Errorf("got %s, want %s", got, want) 75 | } 76 | } 77 | 78 | func TestRemoveHead(t *testing.T) { 79 | var ll LinkedList[string] 80 | 81 | ll.AddTail(&Node[string]{Value: "ONE"}) 82 | ll.AddTail(&Node[string]{Value: "TWO"}) 83 | ll.AddTail(&Node[string]{Value: "THREE"}) 84 | 85 | ll.RemoveHead() 86 | 87 | want := "HEAD->TWO->THREE->TAIL" 88 | got := ll.String() 89 | 90 | if got != want { 91 | t.Errorf("got %s, want %s", got, want) 92 | } 93 | } 94 | 95 | func TestRemoveTail(t *testing.T) { 96 | var ll LinkedList[string] 97 | 98 | ll.AddTail(&Node[string]{Value: "ONE"}) 99 | ll.AddTail(&Node[string]{Value: "TWO"}) 100 | ll.AddTail(&Node[string]{Value: "THREE"}) 101 | 102 | ll.RemoveTail() 103 | 104 | want := "HEAD->ONE->TWO->TAIL" 105 | got := ll.String() 106 | 107 | if got != want { 108 | t.Errorf("got %s, want %s", got, want) 109 | } 110 | } 111 | 112 | func TestEnumerate(t *testing.T) { 113 | var ll LinkedList[string] 114 | 115 | ll.AddTail(&Node[string]{Value: "1"}) 116 | ll.AddTail(&Node[string]{Value: "2"}) 117 | ll.AddTail(&Node[string]{Value: "3"}) 118 | 119 | got := []string{} 120 | 121 | enum := ll.enumerator() 122 | 123 | node := enum.getNext() 124 | for node != nil { 125 | got = append(got, node.Value) 126 | node = enum.getNext() 127 | } 128 | 129 | if got[0] != "1" || got[1] != "2" || got[2] != "3" { 130 | t.Errorf("got [%s, %s, %s], want [1, 2, 3]", got[0], got[1], got[2]) 131 | } 132 | } 133 | -------------------------------------------------------------------------------- /avl_tree/avl_tree.go: -------------------------------------------------------------------------------- 1 | package avl_tree 2 | 3 | import ( 4 | "golang.org/x/exp/constraints" 5 | ) 6 | 7 | type Node[T constraints.Ordered] struct { 8 | leftChild *Node[T] 9 | rightChild *Node[T] 10 | Data T 11 | height int 12 | } 13 | 14 | func NewNode[T constraints.Ordered](data T) *Node[T] { 15 | return &Node[T]{ 16 | height: 1, 17 | Data: data, 18 | } 19 | } 20 | 21 | // AVLTree is an Adelson-Velsky and Landis self-balancing binary search tree. 22 | type AVLTree[T constraints.Ordered] struct { 23 | Root *Node[T] 24 | } 25 | 26 | func NewAVLTree[T constraints.Ordered]() AVLTree[T] { 27 | return AVLTree[T]{} 28 | } 29 | 30 | func max(i, j int) int { 31 | if i > j { 32 | return i 33 | } 34 | return j 35 | } 36 | 37 | func height[T constraints.Ordered](node *Node[T]) int { 38 | if node == nil { 39 | return 0 40 | } 41 | 42 | return node.height 43 | } 44 | 45 | // balanceFactor shows the difference between the left and right 46 | // subtrees of Node n. A difference of more than one would mean 47 | // the balance() function is used to balance the tree 48 | func (n *Node[T]) balanceFactor() int { 49 | if n == nil { 50 | return 0 51 | } 52 | 53 | return height(n.leftChild) - height(n.rightChild) 54 | } 55 | 56 | func rotateRight[T constraints.Ordered](node *Node[T]) *Node[T] { 57 | x := node.leftChild 58 | tmp := x.rightChild 59 | 60 | x.rightChild = node 61 | node.leftChild = tmp 62 | 63 | node.height = max( 64 | height(node.leftChild), 65 | height(node.rightChild), 66 | ) + 1 67 | x.height = max( 68 | height(x.leftChild), 69 | height(x.rightChild), 70 | ) + 1 71 | return x 72 | } 73 | 74 | func rotateLeft[T constraints.Ordered](node *Node[T]) *Node[T] { 75 | y := node.rightChild 76 | tmp := y.leftChild 77 | 78 | y.leftChild = node 79 | node.rightChild = tmp 80 | 81 | node.height = max( 82 | height(node.leftChild), 83 | height(node.rightChild), 84 | ) + 1 85 | 86 | y.height = max( 87 | height(y.leftChild), 88 | height(y.rightChild), 89 | ) + 1 90 | 91 | return y 92 | } 93 | 94 | func insert[T constraints.Ordered](node *Node[T], data T) *Node[T] { 95 | if node == nil { 96 | node = NewNode[T](data) 97 | return node 98 | } 99 | 100 | if data < node.Data { 101 | node.leftChild = insert(node.leftChild, data) 102 | } else if data > node.Data { 103 | node.rightChild = insert(node.rightChild, data) 104 | } else { 105 | return node 106 | } 107 | 108 | node.height = 1 + max(height(node.leftChild), height(node.rightChild)) 109 | 110 | bf := node.balanceFactor() 111 | 112 | if bf > 1 && data < node.leftChild.Data { 113 | return rotateRight(node) 114 | } 115 | 116 | if bf < -1 && data > node.rightChild.Data { 117 | return rotateLeft(node) 118 | } 119 | 120 | if bf > 1 && data > node.leftChild.Data { 121 | node.leftChild = rotateLeft(node.leftChild) 122 | return rotateRight(node) 123 | } 124 | 125 | if bf < -1 && data < node.rightChild.Data { 126 | node.rightChild = rotateRight(node.rightChild) 127 | return rotateLeft(node) 128 | } 129 | 130 | return node 131 | } 132 | 133 | // Add an item to the AVL Tree 134 | func (t *AVLTree[T]) Add(data T) { 135 | t.Root = insert(t.Root, data) 136 | } 137 | 138 | func traverseInOrder[T constraints.Ordered](node *Node[T], data *[]T) { 139 | if node != nil { 140 | traverseInOrder(node.leftChild, data) 141 | *data = append(*data, node.Data) 142 | traverseInOrder(node.rightChild, data) 143 | } 144 | } 145 | 146 | // InOrder tree traversal from Root 147 | func (t *AVLTree[T]) InOrder() []T { 148 | data := []T{} 149 | traverseInOrder(t.Root, &data) 150 | return data 151 | } 152 | -------------------------------------------------------------------------------- /binary_tree/binary_tree.go: -------------------------------------------------------------------------------- 1 | package binary_tree 2 | 3 | import ( 4 | "fmt" 5 | 6 | "golang.org/x/exp/constraints" 7 | ) 8 | 9 | type Node[T constraints.Ordered] struct { 10 | Value T 11 | Left *Node[T] 12 | Right *Node[T] 13 | } 14 | 15 | func (n *Node[T]) GreaterThan(node *Node[T]) bool { 16 | return n.Value > node.Value 17 | } 18 | 19 | func (n *Node[T]) LessThan(node *Node[T]) bool { 20 | return n.Value < node.Value 21 | } 22 | 23 | type BinaryTree[T constraints.Ordered] struct { 24 | Root *Node[T] 25 | Counter int 26 | } 27 | 28 | func new[T constraints.Ordered]() BinaryTree[T] { 29 | return BinaryTree[T]{} 30 | } 31 | 32 | // addTo inserts the item at the correct position given it's 33 | // either less than or greater than its parent. 34 | func (bt *BinaryTree[T]) addTo(node *Node[T], val T) { 35 | nd := Node[T]{ 36 | Value: val, 37 | } 38 | 39 | if nd.LessThan(node) { 40 | if node.Left == nil { 41 | node.Left = &nd 42 | } else { 43 | bt.addTo(node.Left, val) 44 | } 45 | } else { 46 | if node.Right == nil { 47 | node.Right = &nd 48 | } else { 49 | bt.addTo(node.Right, val) 50 | } 51 | } 52 | 53 | } 54 | 55 | // Add an item to the binary tree. 56 | func (bt *BinaryTree[T]) Add(o T) { 57 | if bt.Root == nil { 58 | bt.Root = &Node[T]{ 59 | Value: o, 60 | } 61 | } else { 62 | bt.addTo(bt.Root, o) 63 | } 64 | bt.Counter++ 65 | } 66 | 67 | func (bt *BinaryTree[T]) Contains(val T) bool { 68 | curr, _ := bt.findFromParent(bt.Root, val) 69 | return curr != nil 70 | } 71 | 72 | func (bt *BinaryTree[T]) Remove(val T) error { 73 | node, parent := bt.findFromParent(bt.Root, val) 74 | 75 | if node == nil { 76 | return fmt.Errorf("%v does not exist in tree", val) 77 | } 78 | 79 | // Case 1: Node has no right child so node's left replaces node 80 | if node.Right == nil { 81 | if parent == nil { 82 | bt.Root = node.Left 83 | } else { 84 | if parent.GreaterThan(node) { 85 | parent.Left = node.Left 86 | } else if parent.LessThan(node) { 87 | parent.Right = node.Left 88 | } 89 | } 90 | 91 | // Case 2: Node's right child has no left child so node's right child replaces node 92 | } else if node.Right.Left == nil { 93 | node.Right.Left = node.Left 94 | if parent == nil { 95 | bt.Root = node.Right 96 | } else { 97 | if parent.GreaterThan(node) { 98 | parent.Left = node.Right 99 | } else if parent.LessThan(node) { 100 | parent.Right = node.Right 101 | } 102 | } 103 | 104 | // Case 3 Node's right child has a left child so node's right child's left most child replaces node 105 | } else { 106 | leftMost := node.Right.Left 107 | leftMostParent := node.Right 108 | 109 | for leftMost.Left != nil { 110 | leftMostParent = leftMost 111 | leftMost = leftMost.Left 112 | } 113 | 114 | leftMostParent.Left = leftMost.Right 115 | 116 | leftMost.Left = node.Left 117 | leftMost.Right = node.Right 118 | 119 | if parent == nil { 120 | bt.Root = leftMost 121 | } else { 122 | if parent.GreaterThan(node) { 123 | parent.Left = leftMost 124 | } else if parent.LessThan(node) { 125 | parent.Right = leftMost 126 | } 127 | } 128 | } 129 | 130 | bt.Counter-- 131 | 132 | return nil 133 | } 134 | 135 | func (bt *BinaryTree[T]) findFromParent(node *Node[T], val T) (*Node[T], *Node[T]) { 136 | var parent *Node[T] 137 | find := Node[T]{Value: val} 138 | curr := bt.Root 139 | 140 | for curr != nil { 141 | if find.LessThan(curr) { 142 | parent = curr 143 | curr = curr.Left 144 | } else if find.GreaterThan(curr) { 145 | parent = curr 146 | curr = curr.Right 147 | } else { 148 | break 149 | } 150 | } 151 | 152 | return curr, parent 153 | } 154 | 155 | func (bt *BinaryTree[T]) postOrderTraversal(node *Node[T], vals *[]T) { 156 | var zero *Node[T] 157 | 158 | if node != zero { 159 | bt.postOrderTraversal(node.Left, vals) 160 | bt.postOrderTraversal(node.Right, vals) 161 | *vals = append(*vals, node.Value) 162 | } 163 | } 164 | 165 | // ValuesPostOrder returns the values from the tree after performing an 166 | // postorder traversal: 167 | // 1. Traverse the left subtree 168 | // 2. Traverse the right subtree 169 | // 3. Obtain the value 170 | func (bt *BinaryTree[T]) ValuesPostOrder(node *Node[T]) []T { 171 | values := []T{} 172 | bt.postOrderTraversal(node, &values) 173 | return values 174 | } 175 | 176 | func (bt *BinaryTree[T]) preOrderTraversal(node *Node[T], vals *[]T) { 177 | var zero *Node[T] 178 | 179 | if node != zero { 180 | *vals = append(*vals, node.Value) 181 | bt.preOrderTraversal(node.Left, vals) 182 | bt.preOrderTraversal(node.Right, vals) 183 | } 184 | } 185 | 186 | // ValuesPreOrder returns the values from the tree after performing an 187 | // preorder traversal: 188 | // 1. Obtain the value 189 | // 2. Traverse the left subtree 190 | // 3. Traverse the right subtree 191 | func (bt *BinaryTree[T]) ValuesPreOrder(node *Node[T]) []T { 192 | values := []T{} 193 | bt.preOrderTraversal(node, &values) 194 | return values 195 | } 196 | 197 | func (bt *BinaryTree[T]) inOrderTraversal(node *Node[T], vals *[]T) { 198 | // var zero *Node[T] 199 | 200 | if node != nil { 201 | bt.inOrderTraversal(node.Left, vals) 202 | *vals = append(*vals, node.Value) 203 | bt.inOrderTraversal(node.Right, vals) 204 | } 205 | } 206 | 207 | // ValuesInOrder returns the values from the tree after performing an 208 | // inorder traversal: 209 | // 1. Traverse the left subtree 210 | // 2. Obtain the value 211 | // 3. Traverse the right subtree 212 | func (bt *BinaryTree[T]) ValuesInOrder(node *Node[T]) []T { 213 | values := []T{} 214 | bt.inOrderTraversal(node, &values) 215 | return values 216 | } 217 | -------------------------------------------------------------------------------- /binary_tree/binary_tree_test.go: -------------------------------------------------------------------------------- 1 | package binary_tree 2 | 3 | import ( 4 | "testing" 5 | ) 6 | 7 | func TestContains(t *testing.T) { 8 | tree := new[int]() 9 | 10 | tree.Add(1) 11 | tree.Add(2) 12 | tree.Add(3) 13 | 14 | want := 3 15 | 16 | if !tree.Contains(want) { 17 | t.Errorf("%d not found in tree", want) 18 | } 19 | } 20 | 21 | func TestRemoveLeftReplacesNodeParentNil(t *testing.T) { 22 | tree := new[int]() 23 | 24 | tree.Add(1) 25 | tree.Add(2) 26 | tree.Add(3) 27 | 28 | want := 1 29 | 30 | if !tree.Contains(want) { 31 | t.Errorf("%d not found in tree", want) 32 | } 33 | 34 | tree.Remove(want) 35 | 36 | if tree.Contains(want) { 37 | t.Errorf("%d not removed from tree", want) 38 | } 39 | } 40 | 41 | func TestRemoveLeftReplacesNode(t *testing.T) { 42 | tree := new[int]() 43 | 44 | tree.Add(1) 45 | tree.Add(2) 46 | tree.Add(3) 47 | 48 | want := 2 49 | 50 | if !tree.Contains(want) { 51 | t.Errorf("%d not found in tree", want) 52 | } 53 | 54 | tree.Remove(want) 55 | 56 | if tree.Contains(want) { 57 | t.Errorf("%d not removed from tree", want) 58 | } 59 | } 60 | 61 | func TestRemoveRightChildReplace(t *testing.T) { 62 | tree := new[int]() 63 | 64 | tree.Add(3) 65 | tree.Add(2) 66 | tree.Add(1) 67 | 68 | want := 2 69 | 70 | if !tree.Contains(want) { 71 | t.Errorf("%d not found in tree", want) 72 | } 73 | 74 | tree.Remove(want) 75 | 76 | if tree.Contains(want) { 77 | t.Errorf("%d not removed from tree", want) 78 | } 79 | } 80 | 81 | func TestRemoveRightChildLeftmostChildReplace(t *testing.T) { 82 | tree := new[int]() 83 | 84 | tree.Add(3) 85 | tree.Add(6) 86 | tree.Add(8) 87 | tree.Add(7) 88 | tree.Add(9) 89 | 90 | want := 6 91 | 92 | if !tree.Contains(want) { 93 | t.Errorf("%d not found in tree", want) 94 | } 95 | 96 | tree.Remove(want) 97 | 98 | if tree.Contains(want) { 99 | t.Errorf("%d not removed from tree", want) 100 | } 101 | } 102 | 103 | func TestUnbalancedValuesPostOrder(t *testing.T) { 104 | tree := new[int]() 105 | 106 | want := []int{9, 8, 7, 6, 5, 4, 3, 2, 1} 107 | 108 | tree.Add(1) 109 | tree.Add(2) 110 | tree.Add(3) 111 | tree.Add(4) 112 | tree.Add(5) 113 | tree.Add(6) 114 | tree.Add(7) 115 | tree.Add(8) 116 | tree.Add(9) 117 | 118 | got := tree.ValuesPostOrder(tree.Root) 119 | 120 | if got == nil { 121 | t.Error("returned nil values") 122 | } 123 | 124 | for i, v := range got { 125 | if want[i] != got[i] { 126 | t.Errorf("value at %d: want %d, got %d ", i, want[i], v) 127 | } 128 | } 129 | } 130 | 131 | func TestBalancedValuesPostOrder(t *testing.T) { 132 | tree := new[int]() 133 | 134 | want := []int{1, 4, 7, 6, 3, 13, 14, 10, 8} 135 | 136 | tree.Add(8) 137 | tree.Add(3) 138 | tree.Add(10) 139 | tree.Add(1) 140 | tree.Add(6) 141 | tree.Add(14) 142 | tree.Add(4) 143 | tree.Add(7) 144 | tree.Add(13) 145 | 146 | got := tree.ValuesPostOrder(tree.Root) 147 | 148 | if got == nil { 149 | t.Error("returned nil values") 150 | } 151 | 152 | for i, v := range got { 153 | if want[i] != got[i] { 154 | t.Errorf("value at %d: want %d, got %d ", i, want[i], v) 155 | } 156 | } 157 | } 158 | 159 | func TestUnbalancedValuesPreOrder(t *testing.T) { 160 | tree := new[int]() 161 | 162 | want := []int{1, 9, 8, 7, 6, 5, 4, 3, 2} 163 | 164 | tree.Add(1) 165 | tree.Add(2) 166 | tree.Add(3) 167 | tree.Add(4) 168 | tree.Add(5) 169 | tree.Add(6) 170 | tree.Add(7) 171 | tree.Add(8) 172 | tree.Add(9) 173 | 174 | got := tree.ValuesPreOrder(tree.Root) 175 | 176 | if got == nil { 177 | t.Error("returned nil values") 178 | } 179 | 180 | for i, v := range got { 181 | if want[i] != got[i] { 182 | t.Errorf("value at %d: want %d, got %d ", i, want[i], v) 183 | } 184 | } 185 | } 186 | 187 | func TestBalancedValuesPreOrder(t *testing.T) { 188 | tree := new[int]() 189 | 190 | want := []int{8, 1, 4, 7, 6, 3, 13, 14, 10} 191 | 192 | tree.Add(8) 193 | tree.Add(3) 194 | tree.Add(10) 195 | tree.Add(1) 196 | tree.Add(6) 197 | tree.Add(14) 198 | tree.Add(4) 199 | tree.Add(7) 200 | tree.Add(13) 201 | 202 | got := tree.ValuesPreOrder(tree.Root) 203 | 204 | if got == nil { 205 | t.Error("returned nil values") 206 | } 207 | 208 | for i, v := range got { 209 | if want[i] != got[i] { 210 | t.Errorf("value at %d: want %d, got %d ", i, want[i], v) 211 | } 212 | } 213 | } 214 | 215 | func TestUnbalancedValuesInOrder(t *testing.T) { 216 | tree := new[int]() 217 | 218 | want := []int{1, 2, 3, 4, 5, 6, 7, 8, 9} 219 | 220 | tree.Add(1) 221 | tree.Add(2) 222 | tree.Add(3) 223 | tree.Add(4) 224 | tree.Add(5) 225 | tree.Add(6) 226 | tree.Add(7) 227 | tree.Add(8) 228 | tree.Add(9) 229 | 230 | got := tree.ValuesInOrder(tree.Root) 231 | 232 | if got == nil { 233 | t.Error("returned nil values") 234 | } 235 | 236 | for i, v := range got { 237 | if want[i] != got[i] { 238 | t.Errorf("value at %d: want %d, got %d ", i, want[i], v) 239 | } 240 | } 241 | } 242 | 243 | func TestBalancedValuesInOrder(t *testing.T) { 244 | tree := new[int]() 245 | 246 | want := []int{1, 3, 4, 6, 7, 8, 10, 13, 14} 247 | 248 | tree.Add(8) 249 | tree.Add(3) 250 | tree.Add(10) 251 | tree.Add(1) 252 | tree.Add(6) 253 | tree.Add(14) 254 | tree.Add(4) 255 | tree.Add(7) 256 | tree.Add(13) 257 | 258 | got := tree.ValuesInOrder(tree.Root) 259 | 260 | for i, v := range got { 261 | if want[i] != got[i] { 262 | t.Errorf("value at %d: want %d, got %d ", i, want[i], v) 263 | } 264 | } 265 | } 266 | 267 | func TestRemoveNil(t *testing.T) { 268 | tree := new[int]() 269 | err := tree.Remove(3) 270 | 271 | if err == nil { 272 | t.Error("no error from remove empty item") 273 | } 274 | } 275 | 276 | func TestInOrder(t *testing.T) { 277 | tree := new[int]() 278 | 279 | want := []int{2, 3, 4, 6, 8} 280 | 281 | tree.Add(3) 282 | tree.Add(6) 283 | tree.Add(8) 284 | tree.Add(4) 285 | tree.Add(2) 286 | 287 | got := tree.ValuesInOrder(tree.Root) 288 | 289 | for i, v := range got { 290 | if want[i] != got[i] { 291 | t.Errorf("value at %d: want %d, got %d ", i, want[i], v) 292 | } 293 | } 294 | } 295 | 296 | func TestPreOrderValues(t *testing.T) { 297 | tree := new[int]() 298 | 299 | want := []int{3, 2, 6, 4, 8} 300 | 301 | tree.Add(3) 302 | tree.Add(6) 303 | tree.Add(8) 304 | tree.Add(4) 305 | tree.Add(2) 306 | 307 | got := tree.ValuesPreOrder(tree.Root) 308 | 309 | for i, v := range got { 310 | if want[i] != got[i] { 311 | t.Errorf("value at %d: want %d, got %d ", i, want[i], v) 312 | } 313 | } 314 | } 315 | 316 | func TestPostOrderValues(t *testing.T) { 317 | tree := new[int]() 318 | 319 | want := []int{2, 4, 8, 6, 3} 320 | 321 | tree.Add(3) 322 | tree.Add(6) 323 | tree.Add(8) 324 | tree.Add(4) 325 | tree.Add(2) 326 | 327 | got := tree.ValuesPostOrder(tree.Root) 328 | 329 | for i, v := range got { 330 | if want[i] != got[i] { 331 | t.Errorf("value at %d: want %d, got %d ", i, want[i], v) 332 | } 333 | } 334 | } 335 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | GNU AFFERO GENERAL PUBLIC LICENSE 2 | Version 3, 19 November 2007 3 | 4 | Copyright (C) 2007 Free Software Foundation, Inc. 5 | Everyone is permitted to copy and distribute verbatim copies 6 | of this license document, but changing it is not allowed. 7 | 8 | Preamble 9 | 10 | The GNU Affero General Public License is a free, copyleft license for 11 | software and other kinds of works, specifically designed to ensure 12 | cooperation with the community in the case of network server software. 13 | 14 | The licenses for most software and other practical works are designed 15 | to take away your freedom to share and change the works. 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To "grant" such a patent license to a 484 | party means to make such an agreement or commitment not to enforce a 485 | patent against the party. 486 | 487 | If you convey a covered work, knowingly relying on a patent license, 488 | and the Corresponding Source of the work is not available for anyone 489 | to copy, free of charge and under the terms of this License, through a 490 | publicly available network server or other readily accessible means, 491 | then you must either (1) cause the Corresponding Source to be so 492 | available, or (2) arrange to deprive yourself of the benefit of the 493 | patent license for this particular work, or (3) arrange, in a manner 494 | consistent with the requirements of this License, to extend the patent 495 | license to downstream recipients. "Knowingly relying" means you have 496 | actual knowledge that, but for the patent license, your conveying the 497 | covered work in a country, or your recipient's use of the covered work 498 | in a country, would infringe one or more identifiable patents in that 499 | country that you have reason to believe are valid. 500 | 501 | If, pursuant to or in connection with a single transaction or 502 | arrangement, you convey, or propagate by procuring conveyance of, a 503 | covered work, and grant a patent license to some of the parties 504 | receiving the covered work authorizing them to use, propagate, modify 505 | or convey a specific copy of the covered work, then the patent license 506 | you grant is automatically extended to all recipients of the covered 507 | work and works based on it. 508 | 509 | A patent license is "discriminatory" if it does not include within 510 | the scope of its coverage, prohibits the exercise of, or is 511 | conditioned on the non-exercise of one or more of the rights that are 512 | specifically granted under this License. You may not convey a covered 513 | work if you are a party to an arrangement with a third party that is 514 | in the business of distributing software, under which you make payment 515 | to the third party based on the extent of your activity of conveying 516 | the work, and under which the third party grants, to any of the 517 | parties who would receive the covered work from you, a discriminatory 518 | patent license (a) in connection with copies of the covered work 519 | conveyed by you (or copies made from those copies), or (b) primarily 520 | for and in connection with specific products or compilations that 521 | contain the covered work, unless you entered into that arrangement, 522 | or that patent license was granted, prior to 28 March 2007. 523 | 524 | Nothing in this License shall be construed as excluding or limiting 525 | any implied license or other defenses to infringement that may 526 | otherwise be available to you under applicable patent law. 527 | 528 | 12. No Surrender of Others' Freedom. 529 | 530 | If conditions are imposed on you (whether by court order, agreement or 531 | otherwise) that contradict the conditions of this License, they do not 532 | excuse you from the conditions of this License. If you cannot convey a 533 | covered work so as to satisfy simultaneously your obligations under this 534 | License and any other pertinent obligations, then as a consequence you may 535 | not convey it at all. For example, if you agree to terms that obligate you 536 | to collect a royalty for further conveying from those to whom you convey 537 | the Program, the only way you could satisfy both those terms and this 538 | License would be to refrain entirely from conveying the Program. 539 | 540 | 13. Remote Network Interaction; Use with the GNU General Public License. 541 | 542 | Notwithstanding any other provision of this License, if you modify the 543 | Program, your modified version must prominently offer all users 544 | interacting with it remotely through a computer network (if your version 545 | supports such interaction) an opportunity to receive the Corresponding 546 | Source of your version by providing access to the Corresponding Source 547 | from a network server at no charge, through some standard or customary 548 | means of facilitating copying of software. This Corresponding Source 549 | shall include the Corresponding Source for any work covered by version 3 550 | of the GNU General Public License that is incorporated pursuant to the 551 | following paragraph. 552 | 553 | Notwithstanding any other provision of this License, you have 554 | permission to link or combine any covered work with a work licensed 555 | under version 3 of the GNU General Public License into a single 556 | combined work, and to convey the resulting work. The terms of this 557 | License will continue to apply to the part which is the covered work, 558 | but the work with which it is combined will remain governed by version 559 | 3 of the GNU General Public License. 560 | 561 | 14. Revised Versions of this License. 562 | 563 | The Free Software Foundation may publish revised and/or new versions of 564 | the GNU Affero General Public License from time to time. Such new versions 565 | will be similar in spirit to the present version, but may differ in detail to 566 | address new problems or concerns. 567 | 568 | Each version is given a distinguishing version number. If the 569 | Program specifies that a certain numbered version of the GNU Affero General 570 | Public License "or any later version" applies to it, you have the 571 | option of following the terms and conditions either of that numbered 572 | version or of any later version published by the Free Software 573 | Foundation. If the Program does not specify a version number of the 574 | GNU Affero General Public License, you may choose any version ever published 575 | by the Free Software Foundation. 576 | 577 | If the Program specifies that a proxy can decide which future 578 | versions of the GNU Affero General Public License can be used, that proxy's 579 | public statement of acceptance of a version permanently authorizes you 580 | to choose that version for the Program. 581 | 582 | Later license versions may give you additional or different 583 | permissions. However, no additional obligations are imposed on any 584 | author or copyright holder as a result of your choosing to follow a 585 | later version. 586 | 587 | 15. Disclaimer of Warranty. 588 | 589 | THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY 590 | APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT 591 | HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY 592 | OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, 593 | THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 594 | PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM 595 | IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF 596 | ALL NECESSARY SERVICING, REPAIR OR CORRECTION. 597 | 598 | 16. Limitation of Liability. 599 | 600 | IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING 601 | WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS 602 | THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY 603 | GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE 604 | USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF 605 | DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD 606 | PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), 607 | EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF 608 | SUCH DAMAGES. 609 | 610 | 17. Interpretation of Sections 15 and 16. 611 | 612 | If the disclaimer of warranty and limitation of liability provided 613 | above cannot be given local legal effect according to their terms, 614 | reviewing courts shall apply local law that most closely approximates 615 | an absolute waiver of all civil liability in connection with the 616 | Program, unless a warranty or assumption of liability accompanies a 617 | copy of the Program in return for a fee. 618 | 619 | END OF TERMS AND CONDITIONS 620 | 621 | How to Apply These Terms to Your New Programs 622 | 623 | If you develop a new program, and you want it to be of the greatest 624 | possible use to the public, the best way to achieve this is to make it 625 | free software which everyone can redistribute and change under these terms. 626 | 627 | To do so, attach the following notices to the program. It is safest 628 | to attach them to the start of each source file to most effectively 629 | state the exclusion of warranty; and each file should have at least 630 | the "copyright" line and a pointer to where the full notice is found. 631 | 632 | 633 | Copyright (C) 634 | 635 | This program is free software: you can redistribute it and/or modify 636 | it under the terms of the GNU Affero General Public License as published 637 | by the Free Software Foundation, either version 3 of the License, or 638 | (at your option) any later version. 639 | 640 | This program is distributed in the hope that it will be useful, 641 | but WITHOUT ANY WARRANTY; without even the implied warranty of 642 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 643 | GNU Affero General Public License for more details. 644 | 645 | You should have received a copy of the GNU Affero General Public License 646 | along with this program. If not, see . 647 | 648 | Also add information on how to contact you by electronic and paper mail. 649 | 650 | If your software can interact with users remotely through a computer 651 | network, you should also make sure that it provides a way for users to 652 | get its source. For example, if your program is a web application, its 653 | interface could display a "Source" link that leads users to an archive 654 | of the code. There are many ways you could offer source, and different 655 | solutions will be better for different programs; see section 13 for the 656 | specific requirements. 657 | 658 | You should also get your employer (if you work as a programmer) or school, 659 | if any, to sign a "copyright disclaimer" for the program, if necessary. 660 | For more information on this, and how to apply and follow the GNU AGPL, see 661 | . 662 | --------------------------------------------------------------------------------