refactor: contains-duplicate solution

Author: sm9171

contains-duplicate/sm9171.java

@@ -3,12 +3,11 @@ public boolean containsDuplicate(int[] nums) {
         HashSet<Integer> set = new HashSet<>();
 
         for (int i = 0; i < nums.length; i++) {
+            if (set.contains(nums[i])) {
+                return true;
+            }
             set.add(nums[i]);
         }
-
-        if (nums.length == set.size()) {
-            return false;
-        }
-        return true;
+        return false;
     }
 }