feat:contains-duplicate solution

Author: sm9171

contains-duplicate/sm9171.java

@@ -0,0 +1,14 @@
+class Solution {
+    public boolean containsDuplicate(int[] nums) {
+        HashSet<Integer> set = new HashSet<>();
+
+        for (int i = 0; i < nums.length; i++) {
+            set.add(nums[i]);
+        }
+
+        if (nums.length == set.size()) {
+            return false;
+        }
+        return true;
+    }
+}