diff --git a/contains-duplicate/Cyjin-jani.js b/contains-duplicate/Cyjin-jani.js
new file mode 100644
index 0000000000..304b042b68
--- /dev/null
+++ b/contains-duplicate/Cyjin-jani.js
@@ -0,0 +1,4 @@
+const containsDuplicate = function (nums) {
+  const data = new Set(nums);
+  return data.size !== nums.length;
+};
diff --git a/house-robber/Cyjin-jani.js b/house-robber/Cyjin-jani.js
new file mode 100644
index 0000000000..53270e3b76
--- /dev/null
+++ b/house-robber/Cyjin-jani.js
@@ -0,0 +1,11 @@
+const rob = function (nums) {
+  // 최대 누적값을 저장하는 배열
+  const data = [];
+  data[0] = nums[0];
+
+  for (let i = 1; i < nums.length; i++) {
+    data[i] = Math.max(data[i - 1], (data[i - 2] ?? 0) + nums[i]);
+  }
+
+  return data[data.length - 1];
+};
diff --git a/longest-consecutive-sequence/Cyjin-jani.js b/longest-consecutive-sequence/Cyjin-jani.js
new file mode 100644
index 0000000000..fc730e379f
--- /dev/null
+++ b/longest-consecutive-sequence/Cyjin-jani.js
@@ -0,0 +1,22 @@
+var longestConsecutive = function (nums) {
+  // 숫자 존재 유무를 확인할 수 있는 자료구조 세팅
+  const dataSet = new Set(nums);
+  let answer = 0;
+
+  // 전체 숫자를 순회하면서 시작점을 확인
+  for (let num of dataSet) {
+    // num - 1이 dataSet에 있는지 확인. 있다면 시작점이 아니므로 패스
+    if (!dataSet.has(num - 1)) {
+      // 없다면 시작점. 여기서부터 연속된 숫자가 얼마나 있는지 카운팅.
+      let count = 1;
+      let target = num;
+      while (dataSet.has(target + 1)) {
+        count++;
+        target++;
+      }
+      // longest를 구하는 문제이므로 max로 더 긴 답을 판단
+      answer = Math.max(count, answer);
+    }
+  }
+  return answer;
+};
diff --git a/top-k-frequent-elements/Cyjin-jani.js b/top-k-frequent-elements/Cyjin-jani.js
new file mode 100644
index 0000000000..7c1a2d8813
--- /dev/null
+++ b/top-k-frequent-elements/Cyjin-jani.js
@@ -0,0 +1,23 @@
+const topKFrequent = function (nums, k) {
+  const tempArr = Array.from({ length: nums.length }, () => []);
+  const obj = {};
+
+  for (let num of nums) {
+    obj[num] = (obj[num] || 0) + 1;
+  }
+
+  for (let key in obj) {
+    const val = obj[key] - 1;
+    tempArr[val].push(+key);
+  }
+
+  // answer.flat(), return answer.slice(-k) 대신 좀 더 최적화된 코드로 변경합니다.
+  const answer = [];
+  for (let i = tempArr.length - 1; i >= 0; i--) {
+    for (let num of tempArr[i]) {
+      answer.push(num);
+      if (answer.length === k) return answer;
+    }
+  }
+  return answer;
+};
diff --git a/two-sum/Cyjin-jani.js b/two-sum/Cyjin-jani.js
new file mode 100644
index 0000000000..a450ae29d8
--- /dev/null
+++ b/two-sum/Cyjin-jani.js
@@ -0,0 +1,14 @@
+const twoSum = function (nums, target) {
+  let memo = {};
+
+  for (let i = 0; i < nums.length; i++) {
+    let current = nums[i];
+    let needed = target - current;
+
+    if (needed in memo) {
+      return [memo[needed], i];
+    }
+
+    memo[current] = i;
+  }
+};