From 1e078777e78a982dd8248c1a0a89604dc227d212 Mon Sep 17 00:00:00 2001
From: Gajay <6947656+GAjay@users.noreply.github.com>
Date: Wed, 21 Oct 2026 01:30:42 +0000
Subject: [PATCH] feat(daily): implement 2026-10-21 contains-duplicate

---
 automation/state.json                         |  4 ++--
 .../2026-10-21-contains-duplicate/README.md   | 24 +++++++++++++++++++
 .../contains-duplicate.test.js                | 17 +++++++++++++
 .../2026-10-21-contains-duplicate/solution.js | 12 ++++++++++
 4 files changed, 55 insertions(+), 2 deletions(-)
 create mode 100644 problems/2026-10-21-contains-duplicate/README.md
 create mode 100644 problems/2026-10-21-contains-duplicate/contains-duplicate.test.js
 create mode 100644 problems/2026-10-21-contains-duplicate/solution.js

diff --git a/automation/state.json b/automation/state.json
index cdd93c1..b4dc476 100644
--- a/automation/state.json
+++ b/automation/state.json
@@ -1,4 +1,4 @@
 {
-  "catalogIndex": 1,
-  "lastRunDate": "2026-10-20"
+  "catalogIndex": 2,
+  "lastRunDate": "2026-10-21"
 }
diff --git a/problems/2026-10-21-contains-duplicate/README.md b/problems/2026-10-21-contains-duplicate/README.md
new file mode 100644
index 0000000..ad57435
--- /dev/null
+++ b/problems/2026-10-21-contains-duplicate/README.md
@@ -0,0 +1,24 @@
+# Contains Duplicate
+
+## Problem
+
+Given an integer array `nums`, return `true` if any value appears **at least twice** in the array, and return `false` if every element is distinct.
+
+## Examples
+
+```
+Input: nums = [1, 2, 3, 1]
+Output: true
+
+Input: nums = [1, 2, 3, 4]
+Output: false
+```
+
+## Constraints
+
+- `1 <= nums.length <= 10^5`
+- `-10^9 <= nums[i] <= 10^9`
+
+## Notes
+
+Implement `containsDuplicate` in `solution.js`.
diff --git a/problems/2026-10-21-contains-duplicate/contains-duplicate.test.js b/problems/2026-10-21-contains-duplicate/contains-duplicate.test.js
new file mode 100644
index 0000000..2855b40
--- /dev/null
+++ b/problems/2026-10-21-contains-duplicate/contains-duplicate.test.js
@@ -0,0 +1,17 @@
+import { describe, it } from "node:test";
+import assert from "node:assert/strict";
+import { containsDuplicate } from "./solution.js";
+
+describe("containsDuplicate", () => {
+  it("has duplicate", () => {
+    assert.equal(containsDuplicate([1,2,3,1]), true);
+  });
+
+  it("all unique", () => {
+    assert.equal(containsDuplicate([1,2,3,4]), false);
+  });
+
+  it("duplicate at end", () => {
+    assert.equal(containsDuplicate([1,1]), true);
+  });
+});
diff --git a/problems/2026-10-21-contains-duplicate/solution.js b/problems/2026-10-21-contains-duplicate/solution.js
new file mode 100644
index 0000000..2b805f1
--- /dev/null
+++ b/problems/2026-10-21-contains-duplicate/solution.js
@@ -0,0 +1,12 @@
+/**
+ * @param {number[]} nums
+ * @returns {boolean}
+ */
+export function containsDuplicate(nums) {
+  const seen = new Set();
+  for (const n of nums) {
+    if (seen.has(n)) return true;
+    seen.add(n);
+  }
+  return false;
+}