solve contains duplicate problem

Author: sora0319

contains-duplicate/sora0319.java

@@ -1,4 +1,21 @@
 import java.util.*;
+// 개선 방향
+class Solution {
+    public boolean containsDuplicate(int[] nums) {
+        Set duplication = new HashSet<>();
+
+        for(int n : nums){
+            if(duplication.contains(n)){
+               return true;
+            }
+            duplication.add(n);
+        }
+        return false;
+    }
+}
+
+
+// 초기 문제 풀이
 class Solution {
     public boolean containsDuplicate(int[] nums) {
         Arrays.sort(nums);