diff --git a/contains-duplicate/jeongwoo903.js b/contains-duplicate/jeongwoo903.js
new file mode 100644
index 000000000..8454779c6
--- /dev/null
+++ b/contains-duplicate/jeongwoo903.js
@@ -0,0 +1,11 @@
+/**
+ * @param {number[]} nums
+ * @return {boolean}
+ */
+
+var containsDuplicate = function(nums) {
+  const originalLength = nums.length;
+  const parsedLength = new Set(nums).size;
+
+  return originalLength !== parsedLength;
+};
diff --git a/house-robber/jeongwoo903.js b/house-robber/jeongwoo903.js
new file mode 100644
index 000000000..b94456ab3
--- /dev/null
+++ b/house-robber/jeongwoo903.js
@@ -0,0 +1,19 @@
+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+
+// dp 개념을 이용
+
+var rob = function(nums) {
+  if(nums.length == 0) { return 0 };
+  if(nums.length == 1) { return nums[0] };
+
+  nums[1] = Math.max(nums[0], nums[1]);
+
+  for(let i = 2; i < nums.length; i++) {
+    nums[i] = Math.max(nums[i-2] + nums[i], nums[i-1])
+  }
+
+  return nums[nums.length - 1];
+};
diff --git a/longest-consecutive-sequence/jeongwoo903.js b/longest-consecutive-sequence/jeongwoo903.js
new file mode 100644
index 000000000..06f390ae3
--- /dev/null
+++ b/longest-consecutive-sequence/jeongwoo903.js
@@ -0,0 +1,25 @@
+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+
+var longestConsecutive = function(nums) {
+    if (nums.length <= 1) return nums.length;
+
+    const sortedArray = [...new Set(nums)].sort((a,b) => a - b);
+
+    let maxLength = 1;
+    let currentLength = 1;
+
+    for (let i = 1; i < sortedArray.length; i++) {
+        if (sortedArray[i] === sortedArray[i-1] + 1) {
+            currentLength++;
+        } else {
+            currentLength = 1;
+        }
+
+        maxLength = Math.max(maxLength, currentLength);
+    }
+
+    return maxLength;
+};
diff --git a/top-k-frequent-elements/jeongwoo903.js b/top-k-frequent-elements/jeongwoo903.js
new file mode 100644
index 000000000..97f1232bb
--- /dev/null
+++ b/top-k-frequent-elements/jeongwoo903.js
@@ -0,0 +1,20 @@
+/**
+ * @param {number[]} nums
+ * @param {number} k
+ * @return {number[]}
+ */
+var topKFrequent = function(nums, k) {
+  // Map을 통해 nums의 담긴 숫자들의 빈번함을 정리함.
+  const frequencyMap = nums.reduce((map, num) => {
+    map.set(num, (map.get(num) || 0) + 1);
+    return map;
+  }, new Map());
+
+  // 빈도수를 기준으로 정렬하여 답을 유도함.
+  const result = Array.from(frequencyMap.entries())
+  .sort((a, b) => b[1] - a[1])
+  .slice(0, k)
+  .map(item => item[0]);
+
+  return result;
+};
diff --git a/two-sum/jeongwoo903.js b/two-sum/jeongwoo903.js
new file mode 100644
index 000000000..1144c727a
--- /dev/null
+++ b/two-sum/jeongwoo903.js
@@ -0,0 +1,20 @@
+/**
+ * @param {number[]} nums
+ * @param {number} target
+ * @return {number[]}
+ */
+var twoSum = function(nums, target) {
+    const numMap = new Map();
+
+    for (let i= 0 ; i < nums.length ; i++ ) {
+        let complement = target - nums[i];
+
+        if (numMap.has(complement)) {
+            return [numMap.get(complement), i];
+        }
+
+        numMap.set(nums[i], i);
+    }
+
+    return [];
+};