Merge pull request #60 from luiz-mai/levenshtein-distance

Levenshtein distance

Author: 0xbrayo

strings/levenshteinDistance.go

@@ -0,0 +1,73 @@
+/*
+This algorithm calculates the distance between two strings.
+Parameters: two strings to compare and weights of insertion, substitution and deletion.
+Output: distance between both strings
+*/
+
+package main
+
+import (
+	"fmt"
+)
+
+func levenshteinDistance(str1, str2 string, icost, scost, dcost int) int {
+	row1 := make([]int, len(str2)+1)
+	row2 := make([]int, len(str2)+1)
+	var tmp []int
+
+	for i := 1; i <= len(str2); i++ {
+		row1[i] = i * icost
+	}
+
+	for i := 1; i <= len(str1); i++ {
+		row2[0] = i * dcost
+
+		for j := 1; j <= len(str2); j++ {
+			if str1[i-1] == str2[j-1] {
+				row2[j] = row1[j-1]
+			} else {
+				ins := row2[j-1] + icost
+				del := row1[j] + dcost
+				sub := row1[j-1] + scost
+
+				if ins < del && ins < sub {
+					row2[j] = ins
+				} else if del < sub {
+					row2[j] = del
+				} else {
+					row2[j] = sub
+				}
+			}
+		}
+
+		tmp = row1
+		row1 = row2
+		row2 = tmp
+	}
+
+	return row1[len(row1)-1]
+}
+
+func min(str1, str2 int) int {
+	if str1 < str2 {
+		return str1
+	}
+	return str2
+}
+
+func main() {
+	str1 := "stingy"
+	str2 := "ring"
+
+	// Using weight 1 for insertion, substitution and deletion
+	strDistance1 := levenshteinDistance(str1, str2, 1, 1, 1)
+	fmt.Printf("Distance between \"%s\" and \"%s\" is: %d.\n", str1, str2, strDistance1)
+	// Output: Distance between "stingy" and "ring" is: 3.
+
+	// Using weight 1 for insertion/substitution and weight 3 for deletion
+	strDistance2 := levenshteinDistance(str1, str2, 1, 1, 3)
+	fmt.Printf("Distance between \"%s\" and \"%s\" is: %d.\n", str1, str2, strDistance2)
+	// Output: Distance between "stingy" and "ring" is: 7.
+
+	return
+}