diff --git a/problems/2026-10-22-max-subarray/README.md b/problems/2026-10-22-max-subarray/README.md
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+# Maximum Subarray
+
+## Problem
+
+Given an integer array `nums`, find the subarray with the largest sum, and return its sum.
+
+## Examples
+
+```
+Input: nums = [-2, 1, -3, 4, -1, 2, 1, -5, 4]
+Output: 6
+Explanation: [4, -1, 2, 1] has sum 6.
+```
+
+## Constraints
+
+- `1 <= nums.length <= 10^5`
+- `-10^4 <= nums[i] <= 10^4`
+
+## Notes
+
+Implement `maxSubArray` in `solution.js`.
diff --git a/problems/2026-10-22-max-subarray/max-subarray.test.js b/problems/2026-10-22-max-subarray/max-subarray.test.js
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+import { describe, it } from "node:test";
+import assert from "node:assert/strict";
+import { maxSubArray } from "./solution.js";
+
+describe("maxSubArray", () => {
+  it("classic kadane", () => {
+    assert.equal(maxSubArray([-2,1,-3,4,-1,2,1,-5,4]), 6);
+  });
+
+  it("single element", () => {
+    assert.equal(maxSubArray([1]), 1);
+  });
+
+  it("all negative pick max", () => {
+    assert.equal(maxSubArray([-2,-1]), -1);
+  });
+});
diff --git a/problems/2026-10-22-max-subarray/solution.js b/problems/2026-10-22-max-subarray/solution.js
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+/**
+ * @param {number[]} nums
+ * @returns {number}
+ */
+export function maxSubArray(nums) {
+  let best = nums[0];
+  let cur = nums[0];
+  for (let i = 1; i < nums.length; i++) {
+    cur = Math.max(nums[i], cur + nums[i]);
+    best = Math.max(best, cur);
+  }
+  return best;
+}