Add more randomness to the answer

padlock-impl/src/main/java/com/cleverthis/interview/padlock/PadlockImpl.java

@@ -55,7 +55,9 @@ public class PadlockImpl {
         List<Integer> answer = new ArrayList<>(numpadSize);
         for (int i = 0; i < numpadSize; i++)
             answer.add(i);
+        for (int i = 0; i < numpadSize / 2; i++) {
             Collections.shuffle(answer);
+        }
         this.correctPasscode = answer.toArray(new Integer[0]);
     }