[20230921] 이건화 287. Find the Duplicate Number

problems/[230921] 287. Find the Duplicate Number.js

@@ -0,0 +1,16 @@
+/**
+ * leetcode problem link: https://leetcode.com/problems/find-the-duplicate-number/
+ */
+
+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+const findDuplicate = function (nums) {
+  const set = new Set();
+
+  for (const num of nums) {
+    if (set.has(num)) return num;
+    else set.add(num);
+  }
+};