feat: Implement Levenshtein with tests

src/algorithms/levenshtein/__tests__/levenshtein.test.ts

@@ -0,0 +1,16 @@
+import { lev, levW } from "../";
+
+test("lev(abc, abd) == 1", () => {
+    expect(lev("abc", "abd", 3, 3)).toBe(1);
+    expect(levW("abc", "abd")).toBe(1);
+});
+
+test("lev(abc, abcd) == 1", () => {
+    expect(lev("abc", "abcd", 3, 4)).toBe(1);
+    expect(levW("abc", "abcd")).toBe(1);
+});
+
+test("lev(abcd, bcd) == 1", () => {
+    expect(lev("abcd", "bcd", 4, 3)).toBe(1);
+    expect(levW("abcd", "bcd")).toBe(1);
+});

src/algorithms/levenshtein/index.ts

@@ -0,0 +1,30 @@
+export function one(a: string, b: string, i: number, j: number) {
+    if (a[i] === b[j]) {
+        return 0;
+    }
+
+    return 1;
+}
+
+// Computes the difference between the strings a and b.
+// @a, b: The strings to compare
+// @i, j: From where to compare (a_i and b_j)
+// @ret : The distance in insertions, deletions and changes
+export function lev(a: string, b: string, i: number, j: number) {
+    if (Math.min(i, j) === 0) {
+        return Math.max(i, j);
+    } else {
+        return Math.min(
+            lev(a, b, i - 1, j) + 1,
+            lev(a, b, i, j - 1) + 1,
+            lev(a, b, i - 1, j - 1) + one(a, b, i, j)
+        );
+    }
+};
+
+// Computes the difference between the strings a and b.
+// @a, b: The strings to compare
+// @ret : The distance in insertions, deletions and changes
+export function levW(a: string, b: string) {
+    return lev(a, b, a.length, b.length);
+}