add: contains duplicate solution

Author: Tessa1217

contains-duplicate/Tessa1217.java

@@ -0,0 +1,16 @@
+import java.util.HashSet;
+import java.util.Set;
+
+class Solution {
+
+    public boolean containsDuplicate(int[] nums) {
+
+        Set<Integer> distincts = new HashSet<>();
+
+        for (int i = 0; i < nums.length; i++) {
+            distincts.add(nums[i]);
+        }
+
+        return distincts.size() != nums.length;
+    }
+}