diff --git a/contains-duplicate/JisuuungKim.py b/contains-duplicate/JisuuungKim.py
new file mode 100644
index 000000000..c53c740ee
--- /dev/null
+++ b/contains-duplicate/JisuuungKim.py
@@ -0,0 +1,11 @@
+class Solution:
+    def containsDuplicate(self, nums: List[int]) -> bool:
+        count = {}
+
+        for i in nums:
+            if i in count:
+                return True
+            else:
+                count[i] = 1
+
+        return False
diff --git a/two-sum/JisuuungKim.py b/two-sum/JisuuungKim.py
new file mode 100644
index 000000000..5a081b887
--- /dev/null
+++ b/two-sum/JisuuungKim.py
@@ -0,0 +1,12 @@
+class Solution:
+    def twoSum(self, nums: List[int], target: int) -> List[int]:
+        d = {}
+        for i in range(len(nums)):
+            cur = nums[i]
+            x = target - cur
+            if x in d:
+                return [i, d[x]]
+            else:
+                d[cur] = i
+
+    # 시간복잡도 O(n)