wagner-fisher & werner algorithms working

go.mod

@@ -0,0 +1,3 @@
+module git.hafen.run/lukas/edit-distance
+
+go 1.18

helpers.go

@@ -0,0 +1,11 @@
+package editdistance
+
+func min(nums ...int) int {
+	min := nums[0]
+	for _, v := range nums {
+		if v < min {
+			min = v
+		}
+	}
+	return min
+}

helpers_test.go

@@ -0,0 +1,10 @@
+package editdistance
+
+import "testing"
+
+func TestMin(t *testing.T) {
+	mins := min(1, 2, 3, 4, 5)
+	if mins != 1 {
+		t.Errorf("Min was incorrect, got %d, want %d.", mins, 1)
+	}
+}

wagner-fisher.go

@@ -0,0 +1,14 @@
+package editdistance
+
+func WagnerFisher(a, b string) int {
+	if len(a) == 0 {
+		return len(b)
+	}
+	if len(b) == 0 {
+		return len(a)
+	}
+	if a[0] == b[0] {
+		return WagnerFisher(a[1:], b[1:])
+	}
+	return 1 + min(WagnerFisher(a[1:], b), WagnerFisher(a, b[1:]), WagnerFisher(a[1:], b[1:]))
+}

wagner-fisher_test.go

@@ -0,0 +1,11 @@
+package editdistance
+
+import "testing"
+
+func TestWagnerFisher(t *testing.T) {
+	a := "abc"
+	b := "abd"
+	if WagnerFisher(a, b) != 1 {
+		t.Errorf("WagnerFisher was incorrect, got %d, want %d.", WagnerFisher(a, b), 1)
+	}
+}

werner.go

@@ -0,0 +1,45 @@
+package editdistance
+
+import (
+	"strings"
+)
+
+func Werner(a, b string) int {
+
+	phrase_a := strings.Fields(a)
+	phrase_b := strings.Fields(b)
+
+	m := len(phrase_a) + 1
+	n := len(phrase_b) + 1
+	distances := make([][]int, n)
+	for i := range distances {
+		distances[i] = make([]int, m)
+	}
+	// make the inital numbers on the top
+	for i := 1; i < n; i++ {
+		distances[i][0] = i
+	}
+	// make the inital numbers on the left side
+	for i := 1; i < m; i++ {
+		distances[0][i] = i
+	}
+
+	for i := 1; i < n; i++ {
+		for j := 1; j < m; j++ {
+			subCost := 0
+			if strings.EqualFold(phrase_a[j-1], phrase_b[i-1]) {
+				subCost = 0
+			} else {
+				subCost = 1
+			}
+			value := min(
+				distances[i-1][j]+1,
+				distances[i][j-1]+1,
+				distances[i-1][j-1]+subCost,
+			)
+			distances[i][j] = value
+		}
+	}
+
+	return distances[n-1][m-1]
+}

werner_test.go

@@ -0,0 +1,20 @@
+package editdistance
+
+import "testing"
+
+func TestWerner(t *testing.T) {
+
+	a := "a b c"
+	b := "a b d"
+	diff := Werner(a, b)
+	if diff != 1 {
+		t.Errorf("Werner was incorrect, got %d, want %d.", diff, 1)
+	}
+
+	a = "Mary had a little lamb little lamb little lamb."
+	b = "Marry had a little lamb little lab little lamb."
+	diff = Werner(a, b)
+	if diff != 2 {
+		t.Errorf("Werner was incorrect, got %d, want %d.", diff, 2)
+	}
+}