import java.util.Arrays;
import java.util.Random;

public class HasDupEfficiencyTest {
    private static final int NUMBER_OF_TESTS = 100;
    private static final int TEST_ARRAY_LENGTH = 50000;
    private static long startTime = -1;

    public static int[] createRandomSortedArray(int size) {
        Random random = new Random();

        int[] array = new int[size];
        for (int i = 0; i < size; i++) {
            array[i] = random.nextInt(NUMBER_OF_TESTS * TEST_ARRAY_LENGTH);
        }

        Arrays.sort(array);

        return array;
    }

    public static void startTimer() {
        HasDupEfficiencyTest.startTime = System.nanoTime();
    }

    /** pre: startTimer has been called and HasDupEfficiencyTest.startTime != -1 */
    public static long stopTimer() {
        long start = HasDupEfficiencyTest.startTime;

        /* Reset the startTime */
        HasDupEfficiencyTest.startTime = -1; 

        return System.nanoTime() - start;
    }

    /* pre: array.length >= 1 */
    public static long average(long[] array) {
        long average = array[0];
        for (int i = 1; i < array.length; i++) {
            average = (average * i + array[i]) / (i+1);
        }
        return average;
    }

    public static boolean hasDuplicate1(int[] array) {
        for (int i = 0; i < array.length; i++) {
            for (int j = 0; j < array.length; j++) {
                if (i != j && array[i] == array[j]) {
                    return true;
                }
            }
        }
        return false;
    }

    public static boolean hasDuplicate2(int[] array) {
        for (int i = 0; i < array.length - 1; i++) {
            if (array[i] == array[i+1]) {
                return true;
            }
        }
        return false;
    }
 
    public static void main(String[] args) {
        long[] times1 = new long[HasDupEfficiencyTest.NUMBER_OF_TESTS];
        long[] times2 = new long[HasDupEfficiencyTest.NUMBER_OF_TESTS];

        for (int i = 0; i < HasDupEfficiencyTest.NUMBER_OF_TESTS; i++) {
            int[] testArray = createRandomSortedArray(HasDupEfficiencyTest.TEST_ARRAY_LENGTH);
            
            /* Test hasDuplicate1 */
            HasDupEfficiencyTest.startTimer();
            hasDuplicate1(testArray);
            times1[i] = HasDupEfficiencyTest.stopTimer();

            /* Test hasDuplicate2 */
            HasDupEfficiencyTest.startTimer();
            hasDuplicate2(testArray);
            times2[i] = HasDupEfficiencyTest.stopTimer();
        }

        System.out.println("hasDuplicate1 average run time is " + average(times1) + " ns.");
        System.out.println("hasDuplicate2 average run time is " + average(times2) + " ns.");

    }
}