add solution: contains-duplicate

Author: HerrineKim

contains-duplicate/HerrineKim.js

@@ -0,0 +1,16 @@
+// 시간복잡도: O(n)
+
+/**
+ * @param {number[]} nums
+ * @return {boolean}
+ */
+var containsDuplicate = function (nums) {
+  const seen = new Set();
+  for (let num of nums) {
+    if (seen.has(num)) {
+      return true; // 중복 발견
+    }
+    seen.add(num);
+  }
+  return false; // 모든 요소가 고유
+};