169. Majority Element (#111)

Author: Kohei Asai

solutions/majorityElement.test.ts

@@ -0,0 +1,11 @@
+import majorityElement from "./majorityElement";
+
+describe("169. Majority Element", () => {
+  const TEST_CASES = new Map([[[3, 2, 3], 3], [[2, 2, 1, 1, 1, 2, 2], 2]]);
+
+  for (const [nums, expected] of TEST_CASES) {
+    it(`returns ${expected} when calling with [${nums}]`, () => {
+      expect(majorityElement(nums)).toBe(expected);
+    });
+  }
+});

solutions/majorityElement.ts

@@ -0,0 +1,15 @@
+// 169. Majority Element
+// https://leetcode.com/problems/majority-element/
+export default function majorityElement(nums: number[]): number {
+  const counts = new Map();
+
+  for (const num of nums) {
+    const count = (counts.get(num) || 0) + 1;
+
+    if (count >= nums.length / 2) return num;
+
+    counts.set(num, count);
+  }
+
+  throw new Error();
+}