├── README.md
├── concat.py
├── largest.py
└── autocomplete.py


/README.md:
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1 | # Three-Coding-Problems
2 | 
3 | Video explanation at https://www.youtube.com/watch?v=QGVCnjXmrNg
4 | 
5 | Get 100+ more coding videos at http://coderpro.com/
6 | 


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/concat.py:
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 1 | # Concatenate Words
 2 | # Video explanation at https://www.youtube.com/watch?v=QGVCnjXmrNg
 3 | # Get 100+ more coding videos at http://coderpro.com/
 4 | 
 5 | class Solution(object):
 6 |   def findAllConcatenatedWords(self, words):
 7 |     wordDict = set(words)
 8 |     cache = {}
 9 |     return [word for word in words if self._canForm(word, wordDict, cache)]
10 | 
11 |   def _canForm(self, word, wordDict, cache):
12 |     if word in cache:
13 |       return cache[word]
14 |     for index in range(1, len(word)):
15 |       prefix = word[:index]
16 |       suffix = word[index:]
17 |       if prefix in wordDict:
18 |         if suffix in wordDict or self._canForm(suffix, wordDict, cache):
19 |           cache[word] = True
20 |           return True
21 |     cache[word] = False
22 |     return False
23 | 
24 | input = ['cat', 'cats', 'dog', 'catsdog']
25 | print(Solution().findAllConcatenatedWords(input))
26 | # ['catsdog']
27 | 


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/largest.py:
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 1 | # K-th Largest Number
 2 | # Video explanation at https://www.youtube.com/watch?v=QGVCnjXmrNg
 3 | # Get 100+ more coding videos at http://coderpro.com/
 4 | 
 5 | class Solution(object):
 6 |   def findKthLargest(self, arr, k):
 7 |     left = 0
 8 |     right = len(arr) - 1
 9 |     while left <= right:
10 |       pivotIndex = self._partition(arr, left, right)
11 |       if pivotIndex == len(arr) - k:
12 |         return arr[pivotIndex]
13 |       elif pivotIndex > len(arr) - k:
14 |         right = pivotIndex - 1
15 |       else:
16 |         left = pivotIndex + 1
17 |     return -1
18 | 
19 |   def _partition(self, arr, low, high):
20 |     pivot = arr[high]
21 |     index = low
22 |     for j in range(low, high):
23 |       if arr[j] <= pivot:
24 |         arr[index], arr[j] = arr[j], arr[index]
25 |         index += 1
26 |     arr[index], arr[high] = arr[high], arr[index]
27 |     return index
28 | 
29 | 
30 | print(Solution().findKthLargest([5, 7, 2, 3, 4, 1, 6], 3))
31 | # 5
32 | 


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/autocomplete.py:
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 1 | # Autocompletion
 2 | # Video explanation at https://www.youtube.com/watch?v=QGVCnjXmrNg
 3 | # Get 100+ more coding videos at http://coderpro.com/
 4 | 
 5 | class Node:
 6 |   def __init__(self, children, isWord):
 7 |     self.children = children
 8 |     self.isWord = isWord
 9 | 
10 | class Solution:
11 |   def __init__(self):
12 |     self.trie = None
13 | 
14 |   def build(self, words):
15 |     self.trie = Node({}, False)
16 |     for word in words:
17 |       current = self.trie
18 |       for char in word:
19 |         if not char in current.children:
20 |           current.children[char] = Node({}, False)
21 |         current = current.children[char]
22 |       current.isWord = True
23 | 
24 |   def autocomplete(self, prefix):
25 |     current = self.trie
26 |     for char in prefix:
27 |       if not char in current.children:
28 |         return []
29 |       current = current.children[char]
30 |     return self._findWordsFromNode(current, prefix)
31 | 
32 |   def _findWordsFromNode(self, node, prefix):
33 |     words = []
34 |     if node.isWord:
35 |       words += [prefix]
36 |     for char in node.children:
37 |       words += self._findWordsFromNode(node.children[char], prefix + char)
38 |     return words
39 | 
40 | s = Solution()
41 | s.build(['dog', 'dark', 'cat', 'door', 'dodge'])
42 | print(s.autocomplete('do'))
43 | # ['dog', 'door', 'dodge']
44 | 


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