├── README.md
├── go.mod
├── lsd.go
└── lsd_test.go


/README.md:
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 1 | # go-lsd
 2 | 
 3 | Levenshtein String Distance
 4 | 
 5 | ## Usage
 6 | 
 7 | ```
 8 | distnace := lsd.StringDistance("こんにちわ世界", "こにゃにゃちわ世界") // 3
 9 | ```
10 | 
11 | ## Installation
12 | 
13 | ```
14 | $ go get github.com/mattn/go-lsd
15 | ```
16 | 
17 | ## License
18 | 
19 | MIT
20 | 
21 | ## Author
22 | 
23 | Yasuhiro Matsumoto (a.k.a. mattn)
24 | 


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/go.mod:
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1 | module github.com/mattn/go-lsd
2 | 
3 | go 1.15
4 | 


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/lsd.go:
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 1 | package lsd
 2 | 
 3 | func StringDistance(lhs, rhs string) int {
 4 | 	return Distance([]rune(lhs), []rune(rhs))
 5 | }
 6 | 
 7 | func Distance(lhs, rhs []rune) int {
 8 | 	rl1, rl2 := len(lhs), len(rhs)
 9 | 
10 | 	// make distance from the root
11 | 	costs := make([]int, rl1+1)
12 | 	for j := 1; j <= rl1; j++ {
13 | 		costs[j] = j
14 | 	}
15 | 
16 | 	cost, last, prev := 0, 0, 0
17 | 	for i := 1; i <= rl2; i++ {
18 | 		costs[0] = i
19 | 		last = i - 1
20 | 		for j := 1; j <= rl1; j++ {
21 | 			prev = costs[j]
22 | 			cost = 0
23 | 			// previous letter was different
24 | 			if lhs[j-1] != rhs[i-1] {
25 | 				cost = 1
26 | 			}
27 | 			if costs[j]+1 < costs[j-1]+1 {
28 | 				// changes to lhs should be minimum
29 | 				if costs[j]+1 < last+cost {
30 | 					costs[j] = costs[j] + 1
31 | 				} else {
32 | 					costs[j] = last + cost
33 | 				}
34 | 			} else {
35 | 				// changes to rhs should be minimum
36 | 				if costs[j-1]+1 < last+cost {
37 | 					costs[j] = costs[j-1] + 1
38 | 				} else {
39 | 					costs[j] = last + cost
40 | 				}
41 | 			}
42 | 			last = prev
43 | 		}
44 | 	}
45 | 	return costs[rl1]
46 | }
47 | 


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/lsd_test.go:
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 1 | package lsd
 2 | 
 3 | import "testing"
 4 | 
 5 | func TestDistance(t *testing.T) {
 6 | 	var tests = []struct {
 7 | 		lhs  string
 8 | 		rhs  string
 9 | 		want int
10 | 	}{
11 | 		{"こんにちわ世界", "こんにちわ世界", 0},
12 | 		{"こんにちわ世界", "こにゃちわ世界", 2},
13 | 		{"こんにちわ世界", "こにゃにゃちわ世界", 3},
14 | 		{"こんにちわ世界", "こんばんわ世界", 2},
15 | 		{"こんにちわ世界", "こんにちわ", 2},
16 | 		{"こんにちわ世界", "こんばんわ", 4},
17 | 		{"こんにちわ世界", "世界", 5},
18 | 	}
19 | 
20 | 	for _, test := range tests {
21 | 		got := StringDistance(test.lhs, test.rhs)
22 | 		if got != test.want {
23 | 			t.Fatalf("want %v but %v: %v vs %v", test.want, got, test.lhs, test.rhs)
24 | 		}
25 | 	}
26 | }
27 | 


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