diff --git a/contains-duplicate/Kyojin-Hwang.js b/contains-duplicate/Kyojin-Hwang.js
new file mode 100644
index 000000000..d5d17db8a
--- /dev/null
+++ b/contains-duplicate/Kyojin-Hwang.js
@@ -0,0 +1,22 @@
+/**
+ * @param {number[]} nums
+ * @return {boolean}
+ */
+var containsDuplicate = function (nums) {
+  const map = new Map();
+
+  for (let num of nums) {
+    map.set(num, (map.get(num) || 0) + 1);
+  }
+
+  for (let [_, count] of map) {
+    if (count > 1) return true;
+  }
+
+  return false;
+};
+
+// set 방식으로도 대체가능
+// var containsDuplicate = function(nums) {
+//     return new Set(nums).size !== nums.length;
+// };
diff --git a/top-k-frequent-elements/Kyojin-Hwang.js b/top-k-frequent-elements/Kyojin-Hwang.js
new file mode 100644
index 000000000..64d0e7fd3
--- /dev/null
+++ b/top-k-frequent-elements/Kyojin-Hwang.js
@@ -0,0 +1,23 @@
+/**
+ * @param {number[]} nums
+ * @param {number} k
+ * @return {number[]}
+ */
+var topKFrequent = function (nums, k) {
+  const map = new Map();
+  const result = [];
+
+  for (let num of nums) {
+    map.set(num, (map.get(num) || 0) + 1);
+  }
+
+  const sorted = [...map.entries()]
+    .sort((a, b) => b[1] - a[1]) // 빈도 기준으로 정렬
+    .map((entry) => entry[0]); // 숫자만 추출
+
+  for (let i = 0; i < k; i++) {
+    result.push(sorted[i]);
+  }
+
+  return result;
+};
diff --git a/two-sum/Kyojin-Hwang.js b/two-sum/Kyojin-Hwang.js
new file mode 100644
index 000000000..d0814e0ef
--- /dev/null
+++ b/two-sum/Kyojin-Hwang.js
@@ -0,0 +1,18 @@
+/**
+ * @param {number[]} nums
+ * @param {number} target
+ * @return {number[]}
+ */
+var twoSum = function (nums, target) {
+  const map = new Map();
+
+  for (let i = 0; i < nums.length; i++) {
+    const complement = target - nums[i];
+
+    if (map.has(complement)) {
+      return [map.get(complement), i];
+    }
+
+    map.set(nums[i], i);
+  }
+};