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// Package levenshtein is a Go implementation to calculate Levenshtein Distance.
//
// Implementation taken from
// https://gist.github.com/andrei-m/982927#gistcomment-1931258
package levenshtein
// ComputeDistance computes the levenshtein distance between the two
// strings passed as an argument. The return value is the levenshtein distance
//
// Works on runes (Unicode code points) but does not normalize
// the input strings. See https://blog.golang.org/normalization
// and the golang.org/x/text/unicode/norm pacage.
func ComputeDistance(a, b string) int {
if a == b {
return 0
}
// We need to convert to []rune if the strings are non-ascii.
// This could be avoided by using utf8.RuneCountInString
// and then doing some juggling with rune indices.
// The primary challenge is keeping track of the previous rune.
// With a range loop, its not that easy. And with a for-loop
// we need to keep track of the inter-rune width using utf8.DecodeRuneInString
s1 := []rune(a)
s2 := []rune(b)
// swap to save some memory O(min(a,b)) instead of O(a)
if len(s1) > len(s2) {
s1, s2 = s2, s1
}
lenS1 := len(s1)
lenS2 := len(s2)
// init the row
x := make([]int, lenS1+1)
for i := 0; i <= lenS1; i++ {
x[i] = i
}
// fill in the rest
for i := 1; i <= lenS2; i++ {
prev := i
var current int
for j := 1; j <= lenS1; j++ {
if s2[i-1] == s1[j-1] {
current = x[j-1] // match
} else {
current = min(x[j-1]+1, prev+1, x[j]+1)
}
x[j-1] = prev
prev = current
}
x[lenS1] = prev
}
return x[lenS1]
}
func min(a, b, c int) int {
if a < b {
if a < c {
return a
}
} else {
if b < c {
return b
}
}
return c
}
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