diff --git a/contains-duplicate/GUMUNYEONG.js b/contains-duplicate/GUMUNYEONG.js
new file mode 100644
index 000000000..fca1f6f68
--- /dev/null
+++ b/contains-duplicate/GUMUNYEONG.js
@@ -0,0 +1,14 @@
+/**
+ * @param {number[]} nums
+ * @return {boolean}
+ */
+var containsDuplicate = function (nums) {
+    const setObj = new Set(nums);
+
+    const diff = !(nums.length === setObj.size);
+
+    return diff;
+};
+
+// TC: O(n)
+// SC: O(n)
diff --git a/number-of-1-bits/GUMUNYEONG.js b/number-of-1-bits/GUMUNYEONG.js
new file mode 100644
index 000000000..02805653b
--- /dev/null
+++ b/number-of-1-bits/GUMUNYEONG.js
@@ -0,0 +1,17 @@
+/**
+ * @param {number} n
+ * @return {number}
+ */
+var hammingWeight = function (n) {
+    let i = "1";
+
+    while (n > 2) {
+        n % 2 ? i += "1" : "";
+        n = Math.floor(n / 2);
+    }
+
+    return i.length;
+};
+
+// TC: O(log n)
+// SC: O(1)
diff --git a/top-k-frequent-elements/GUMUNYEONG.js b/top-k-frequent-elements/GUMUNYEONG.js
new file mode 100644
index 000000000..0ac4a6f09
--- /dev/null
+++ b/top-k-frequent-elements/GUMUNYEONG.js
@@ -0,0 +1,22 @@
+/**
+ * @param {number[]} nums
+ * @param {number} k
+ * @return {number[]}
+ */
+var topKFrequent = function (nums, k) {
+    let result = [];
+    let fObj = {};
+
+    for (let i = 0; i < nums.length; i++) {
+        const n = nums[i];
+        fObj[n] ? fObj[n]++ : fObj[n] = 1;
+    }
+
+    Object
+        .entries(fObj)
+        .sort((a, b) => b[1] - a[1])
+        .slice(0, k)
+        .filter(v => result.push(v[0]));
+
+    return result;
+};