diff --git a/contains-duplicate/devyejin.py b/contains-duplicate/devyejin.py
index 32b66eabb..d5e15b82a 100644
--- a/contains-duplicate/devyejin.py
+++ b/contains-duplicate/devyejin.py
@@ -1,4 +1,9 @@
-class Solution(object):
-    def containsDuplicate(self, nums):
-        return len(nums) != len(set(nums))
+from typing import List
+"""
+time complexity : O(n)
+space complexity : O(n)
+"""
+class Solution:
+    def containsDuplicate(self, nums: List[int]) -> bool:
+        return len(set(nums)) == len(nums)
 
diff --git a/top-k-frequent-elements/devyejin.py b/top-k-frequent-elements/devyejin.py
index 8a082da5b..6c11d0c30 100644
--- a/top-k-frequent-elements/devyejin.py
+++ b/top-k-frequent-elements/devyejin.py
@@ -1,9 +1,16 @@
+"""
+time complexity: O(nlogn)
+space complexity: O(n)
+"""
+
+from typing import List
 from collections import Counter
-import heapq
+from heapq import nlargest
+
+class Solution:
+    def topKFrequent(self, nums: List[int], k: int) -> List[int]:
+        count = Counter(nums)
+        return [num for num, _ in nlargest(k, count.items(), key=lambda x: x[1])]
 
 
-class Solution(object):
-    def topKFrequent(self, nums, k):
-        counter = sorted(Counter(nums).items(), key=lambda item: -item[1])
-        return list(num for num, count in counter[:k])
 
diff --git a/two-sum/devyejin.py b/two-sum/devyejin.py
index be0dc862d..568a98436 100644
--- a/two-sum/devyejin.py
+++ b/two-sum/devyejin.py
@@ -1,15 +1,12 @@
-class Solution(object):
-    def twoSum(self, nums, target):
+from typing import List
 
-        nums_tuple = sorted(list(enumerate(nums)), key=lambda x: x[1])
-        left, right = 0, len(nums) - 1
 
-        while left < right:
-            temp_sum = nums_tuple[left][1] + nums_tuple[right][1]
-            if temp_sum == target:
-                return [nums_tuple[left][0], nums_tuple[right][0]]
-            elif temp_sum < target:
-                left += 1
-            else:
-                right -= 1
+class Solution:
+    def twoSum(self, nums: List[int], target: int) -> List[int]:
+        seen = {}
+        for idx, num in enumerate(nums):
+            need = target - num
+            if need in seen:
+                return [idx, seen[need]]
+            seen[num] = idx