From ba2afdcc409a7c8e72df030ee7fb5dbef6945462 Mon Sep 17 00:00:00 2001
From: Gajay <6947656+GAjay@users.noreply.github.com>
Date: Sun, 18 Oct 2026 01:30:50 +0000
Subject: [PATCH] feat(daily): implement 2026-10-18 reverse-string

---
 automation/state.json                         |  4 ++--
 problems/2026-10-18-reverse-string/README.md  | 21 +++++++++++++++++++
 .../reverse-string.test.js                    | 21 +++++++++++++++++++
 .../2026-10-18-reverse-string/solution.js     | 15 +++++++++++++
 4 files changed, 59 insertions(+), 2 deletions(-)
 create mode 100644 problems/2026-10-18-reverse-string/README.md
 create mode 100644 problems/2026-10-18-reverse-string/reverse-string.test.js
 create mode 100644 problems/2026-10-18-reverse-string/solution.js

diff --git a/automation/state.json b/automation/state.json
index ecc9f6f..87ed61a 100644
--- a/automation/state.json
+++ b/automation/state.json
@@ -1,4 +1,4 @@
 {
-  "catalogIndex": 6,
-  "lastRunDate": "2026-10-17"
+  "catalogIndex": 7,
+  "lastRunDate": "2026-10-18"
 }
diff --git a/problems/2026-10-18-reverse-string/README.md b/problems/2026-10-18-reverse-string/README.md
new file mode 100644
index 0000000..085e1ec
--- /dev/null
+++ b/problems/2026-10-18-reverse-string/README.md
@@ -0,0 +1,21 @@
+# Reverse String
+
+## Problem
+
+Write a function that reverses a string. The input string is given as an array of characters `s`. You must do this **in-place** with `O(1)` extra memory.
+
+## Examples
+
+```
+Input: s = ["h","e","l","l","o"]
+Output: ["o","l","l","e","h"]
+```
+
+## Constraints
+
+- `1 <= s.length <= 10^5`
+- `s[i]` is a printable ascii character.
+
+## Notes
+
+Implement `reverseString` in `solution.js`.
diff --git a/problems/2026-10-18-reverse-string/reverse-string.test.js b/problems/2026-10-18-reverse-string/reverse-string.test.js
new file mode 100644
index 0000000..fcf4419
--- /dev/null
+++ b/problems/2026-10-18-reverse-string/reverse-string.test.js
@@ -0,0 +1,21 @@
+import { describe, it } from "node:test";
+import assert from "node:assert/strict";
+import { reverseString } from "./solution.js";
+
+describe("reverseString", () => {
+  it("hello", () => {
+    const input = structuredClone(["h","e","l","l","o"]);
+    const args = [["h","e","l","l","o"]];
+    args[0] = input;
+    reverseString(...args);
+    assert.deepEqual(input, ["o","l","l","e","h"]);
+  });
+
+  it("odd length", () => {
+    const input = structuredClone(["a","b","c"]);
+    const args = [["a","b","c"]];
+    args[0] = input;
+    reverseString(...args);
+    assert.deepEqual(input, ["c","b","a"]);
+  });
+});
diff --git a/problems/2026-10-18-reverse-string/solution.js b/problems/2026-10-18-reverse-string/solution.js
new file mode 100644
index 0000000..df6b1d2
--- /dev/null
+++ b/problems/2026-10-18-reverse-string/solution.js
@@ -0,0 +1,15 @@
+/**
+ * @param {string[]} s
+ * @returns {void}
+ */
+export function reverseString(s) {
+  let left = 0;
+  let right = s.length - 1;
+  while (left < right) {
+    const tmp = s[left];
+    s[left] = s[right];
+    s[right] = tmp;
+    left++;
+    right--;
+  }
+}