diff --git a/contains-duplicate/hyeri1ee.java b/contains-duplicate/hyeri1ee.java
new file mode 100644
index 000000000..f746f0268
--- /dev/null
+++ b/contains-duplicate/hyeri1ee.java
@@ -0,0 +1,14 @@
+import java.util.*;
+
+class Solution {
+    Set<Integer> save = new HashSet<>();//O(1)에 이미 등장했는지 판별 위함
+    public boolean containsDuplicate(int[] nums) {
+
+        for(int i=0; i<nums.length; i++){
+            if (!save.contains(nums[i])) save.add(nums[i]);
+            else return true;
+        }
+        return false;
+    }
+}
+
diff --git a/two-sum/Hyeri1ee.java b/two-sum/Hyeri1ee.java
new file mode 100644
index 000000000..c7716502b
--- /dev/null
+++ b/two-sum/Hyeri1ee.java
@@ -0,0 +1,24 @@
+import java.util.*;
+//goal : 두개의 인덱스 반환
+class Solution {
+    static int[] answer = new int[2];
+    public int[] twoSum(int[] nums, int target) {
+        Map<Integer, Integer> maps = new HashMap<>();//num , index
+        for(int i = 0; i < nums.length; i++){
+            int t = target - nums[i]; //새로운 타겟
+            //O(1)으로 다음 부분 찾기
+            if (maps.containsKey(t)){
+                answer[0] = i;
+                answer[1] = maps.get(t);
+
+                Arrays.sort(answer);
+                return answer;
+            }
+
+            maps.put(nums[i], i);
+        }
+
+        return answer;
+
+    }
+}