feat: added test suite + slight changes

damerauLevenshtein.test.ts

@@ -0,0 +1,62 @@
+import { describe, expect, it } from "vitest";
+
+import damerauLevenshtein from "./damerauLevenshtein";
+
+// https://github.com/aldebaran/libport/blob/master/tests/libport/damerau-levenshtein-distance.cc
+
+describe("damerauLevenshtein", () => {
+  const emptyString = "";
+
+  it("should pass, empty strings", () => {
+    const distance = damerauLevenshtein(emptyString, emptyString);
+    // eslint-disable-next-line @typescript-eslint/no-magic-numbers
+    expect(distance).toBe(0);
+  });
+
+  it("should pass, distance 0", () => {
+    const s = "cat";
+    const distance = damerauLevenshtein(s, s);
+    // eslint-disable-next-line @typescript-eslint/no-magic-numbers
+    expect(distance).toBe(0);
+  });
+
+  it("should pass, 100% distance", () => {
+    const s2 = "test";
+    const expectedDistance = s2.length;
+    const distance = damerauLevenshtein(emptyString, s2);
+    expect(distance).toBe(expectedDistance);
+  });
+
+  it("should pass, cat and dog", () => {
+    const distance = damerauLevenshtein("cat", "dog");
+    // eslint-disable-next-line @typescript-eslint/no-magic-numbers
+    expect(distance).toBe(3);
+  });
+
+  it("should pass, deletion", () => {
+    const distance = damerauLevenshtein("azertyuiop", "aeryuop");
+    // eslint-disable-next-line @typescript-eslint/no-magic-numbers
+    expect(distance).toBe(3);
+  });
+
+  it("should pass, insertion", () => {
+    const distance = damerauLevenshtein("aeryuop", "azertyuiop");
+    // eslint-disable-next-line @typescript-eslint/no-magic-numbers
+    expect(distance).toBe(3);
+  });
+
+  it("should pass, substitution", () => {
+    const distance = damerauLevenshtein(
+      "azertyuiopqsdfghjklmwxcvbn,",
+      "qwertyuiopasdfghjkl;zxcvbnm"
+    );
+    // eslint-disable-next-line @typescript-eslint/no-magic-numbers
+    expect(distance).toBe(6);
+  });
+
+  it("should pass, transposition", () => {
+    const distance = damerauLevenshtein("1234567890", "1324576809");
+    // eslint-disable-next-line @typescript-eslint/no-magic-numbers
+    expect(distance).toBe(3);
+  });
+});

damerauLevenshtein.ts

@@ -1,29 +1,37 @@
-export function damerauLevenshtein(s1: string, s2: string): number {
-  const s1len = s1.length;
-  const s2len = s2.length;
-  const matrix: number[][] = Array.from({ length: s1len + 1 }, () => new Array(s2len + 1).fill(0));
+/* eslint-disable @typescript-eslint/no-magic-numbers */
+function damerauLevenshtein(s1: string, s2: string): number {
+  if (s1 === s2) return 0;
 
-  for (let i: number = 1; i <= s1len; i++) {
-    matrix[i][0] = i;
-  }
+  const [s1len, s2len] = [s1.length, s2.length];
+  const matrix: number[][] = Array.from({ length: s1len + 1 }, () =>
+    new Array(s2len + 1).fill(0)
+  );
 
-  for (let j: number = 1; j <= s2len; j++) {
-    matrix[0][j] = j;
-  }
+  for (let y = 1; y <= s1len; y++) matrix[y][0] = y;
+  for (let x = 1; x <= s2len; x++) matrix[0][x] = x;
 
-  for (let i: number = 1; i <= s1len; i++) {
-    for (let j: number = 1; j <= s2len; j++) {
-      if (s1[i - 1] === s2[j - 1]) {
-        matrix[i][j] = matrix[i - 1][j - 1];
+  for (let y = 1; y <= s1len; y++) {
+    for (let x = 1; x <= s2len; x++) {
+      if (s1[y - 1] === s2[x - 1]) {
+        matrix[y][x] = matrix[y - 1][x - 1];
       } else {
-        matrix[i][j] = 1 + Math.min(matrix[i - 1][j], matrix[i][j - 1], matrix[i - 1][j - 1]);
-        if (i > 1 && j > 1 && s1[i - 1] === s2[j - 2] && s1[i - 2] === s2[j - 1]) {
-          matrix[i][j] = Math.min(matrix[i][j], matrix[i - 2][j - 2] + 1);
+        matrix[y][x] =
+          1 +
+          Math.min(matrix[y - 1][x], matrix[y][x - 1], matrix[y - 1][x - 1]);
+        if (
+          y > 1 &&
+          x > 1 &&
+          s1[y - 1] === s2[x - 2] &&
+          s1[y - 2] === s2[x - 1]
+        ) {
+          matrix[y][x] = Math.min(matrix[y][x], matrix[y - 2][x - 2] + 1);
         }
       }
     }
   }
+
   return matrix[s1len][s2len];
 }
+/* eslint-enable @typescript-eslint/no-magic-numbers */
 
 export default damerauLevenshtein;