Daily: 2026-10-24 — Binary Search

automation/state.json

@@ -1,4 +1,4 @@
 {
-  "catalogIndex": 3,
-  "lastRunDate": "2026-10-23"
+  "catalogIndex": 4,
+  "lastRunDate": "2026-10-24"
 }

problems/2026-10-24-binary-search/README.md

@@ -0,0 +1,28 @@
+# Binary Search
+
+## Problem
+
+Given a sorted array of integers `nums` and an integer `target`, return the index of `target` in `nums`, or `-1` if it is not present.
+
+You must write an algorithm with `O(log n)` runtime complexity.
+
+## Examples
+
+```
+Input: nums = [-1, 0, 3, 5, 9, 12], target = 9
+Output: 4
+
+Input: nums = [-1, 0, 3, 5, 9, 12], target = 2
+Output: -1
+```
+
+## Constraints
+
+- `1 <= nums.length <= 10^4`
+- `-10^4 <= nums[i], target <= 10^4`
+- All integers in `nums` are unique.
+- `nums` is sorted ascending.
+
+## Notes
+
+Implement `search` in `solution.js`.

problems/2026-10-24-binary-search/binary-search.test.js

@@ -0,0 +1,17 @@
+import { describe, it } from "node:test";
+import assert from "node:assert/strict";
+import { search } from "./solution.js";
+
+describe("search", () => {
+  it("found", () => {
+    assert.equal(search([-1,0,3,5,9,12], 9), 4);
+  });
+
+  it("not found", () => {
+    assert.equal(search([-1,0,3,5,9,12], 2), -1);
+  });
+
+  it("single hit", () => {
+    assert.equal(search([5], 5), 0);
+  });
+});

problems/2026-10-24-binary-search/solution.js

@@ -0,0 +1,16 @@
+/**
+ * @param {number[]} nums
+ * @param {number} target
+ * @returns {number}
+ */
+export function search(nums, target) {
+  let lo = 0;
+  let hi = nums.length - 1;
+  while (lo <= hi) {
+    const mid = (lo + hi) >> 1;
+    if (nums[mid] === target) return mid;
+    if (nums[mid] < target) lo = mid + 1;
+    else hi = mid - 1;
+  }
+  return -1;
+}