找出数组中唯一的重复元素

package com.coolinkiot.utils;

/**
 * @data Administrator
 * @data 2020/9/2 0002
 */
public class FindDup {

    public static int findDup(int[] arr) {
        if (null == arr) {
            return -1;
        }
        int len = arr.length;
        int res = 0;
        for (int i = 0; i < len; i++) {
            res ^= arr[i];
        }
        for (int i = 1; i < len; i++) {
            res ^= i;
        }
        return res;
    }

    public static void main(String[] args) {
        int[] arr = {1, 3, 4, 2, 5, 3};
        System.out.println(findDup(arr));
    }

}