diff --git a/contains-duplicate/b41-41.ts b/contains-duplicate/b41-41.ts
new file mode 100644
index 000000000..9d6935160
--- /dev/null
+++ b/contains-duplicate/b41-41.ts
@@ -0,0 +1,15 @@
+// nums에 중복이 있는 지 확인하는 것
+// array써서 시간 통과 못했다가 Set 객체로 변경해서 통과
+function containsDuplicate(nums: number[]): boolean {
+    const numSet = new Set();
+
+    for(let num of nums) {
+        if(numSet.has(num)) {
+            return true;
+        } else {
+            numSet.add(num);
+        }
+    }
+
+    return false;
+};
diff --git a/longest-consecutive-sequence/b41-41.ts b/longest-consecutive-sequence/b41-41.ts
new file mode 100644
index 000000000..26d008f68
--- /dev/null
+++ b/longest-consecutive-sequence/b41-41.ts
@@ -0,0 +1,24 @@
+function longestConsecutive(nums: number[]): number {
+    const sortedNums = [...new Set(nums.sort((a, b) => a - b))];
+    const numSet = new Set();
+
+    let dummy: number[] = [];
+
+    for (let i: number = 0; i < sortedNums.length; i++) {
+        const isConsecutiveSequence = sortedNums[i + 1] - sortedNums[i] === 1;
+        const num = sortedNums[i];
+
+        if(!isConsecutiveSequence) {
+            dummy.push(num)
+            numSet.add(dummy.length);
+            dummy = [];
+        } else {
+            dummy.push(num);
+        }
+    }
+    
+    numSet.add(dummy.length);
+    
+    const result = [...numSet].sort((a, b) => Number(b) - Number(a)) as number[];
+    return result[0] || 0;
+}
diff --git a/top-k-frequent-elements/b41-41.ts b/top-k-frequent-elements/b41-41.ts
new file mode 100644
index 000000000..231983557
--- /dev/null
+++ b/top-k-frequent-elements/b41-41.ts
@@ -0,0 +1,17 @@
+function topKFrequent(nums: number[], k: number): number[] {
+    const numMap = new Map();
+
+    for (let num of nums) {
+        if(!numMap.has(num)) {
+            numMap.set(num, 1);
+        } else {
+            const count = Number(numMap.get(num)) || 0;
+            numMap.set(num, count + 1);
+        }
+    }
+
+    const result = [...numMap].sort((a, b) => b[1] - a[1]).map((num) => num[0]).slice(0, k);
+    
+
+    return result;
+};
diff --git a/two-sum/b41-41.ts b/two-sum/b41-41.ts
new file mode 100644
index 000000000..90c8e954b
--- /dev/null
+++ b/two-sum/b41-41.ts
@@ -0,0 +1,26 @@
+// 1차 시도
+// function twoSum(nums: number[], target: number): number[] {
+//     for(const index in nums) {
+//         for(const index2 in nums) {
+//             if (index !== index2) {
+//                 if(target === nums[index] + nums[index2]) {
+//                     return [Number(index), Number(index2)]  
+//                 }
+//             }
+//         }
+//     }
+// };
+
+// 2차 시도
+function twoSum(nums: number[], target: number): number[] {
+    for (const index in nums) {
+        for (let index2 = Number(index) + 1; index2 < nums.length; index2++) {
+            if(target === nums[index] + nums[index2]) {
+                return [Number(index), Number(index2)]
+            }
+        }
+         
+    }
+
+	return [];
+};