1143. Longest Common Subsequence (axross#146)

Author: Kohei Asai

solutions/longest_common_subsequence.ts

@@ -0,0 +1,26 @@
+// 1143. Longest Common Subsequence
+// https://leetcode.com/problems/longest-common-subsequence/
+export default function longestCommonSubsequence(
+  text1: string,
+  text2: string
+): number {
+  const memo = new Map();
+
+  function recurse(i1: number, i2: number): number {
+    if (i1 === text1.length || i2 === text2.length) return 0;
+
+    const key = i1 + i2 * text1.length;
+
+    if (!memo.has(key)) {
+      if (text1[i1] === text2[i2]) {
+        memo.set(key, 1 + recurse(i1 + 1, i2 + 1));
+      } else {
+        memo.set(key, Math.max(recurse(i1 + 1, i2), recurse(i1, i2 + 1)));
+      }
+    }
+
+    return memo.get(key);
+  }
+
+  return recurse(0, 0);
+}

solutions/longest_common_subsequence_test.ts

@@ -0,0 +1,9 @@
+import { test } from "https://deno.land/std/testing/mod.ts";
+import { assertStrictEq } from "https://deno.land/std/testing/asserts.ts";
+import longestCommonSubsequence from "./longest_common_subsequence.ts";
+
+test("1143. Longest Common Subsequence", () => {
+  assertStrictEq(longestCommonSubsequence("abcde", "ace"), 3);
+  assertStrictEq(longestCommonSubsequence("abc", "abc"), 3);
+  assertStrictEq(longestCommonSubsequence("abc", "def"), 0);
+});