解题思路

位运算

diff &= -diff 得到出 diff 最右侧不为 0 的位，也就是不存在重复的两个元素在位级表示上最右侧不同的那一位，利用这一位就可以将两个元素区分开来。

 public int[] singleNumber(int[] nums) {
        int diff = 0;
        int[] res = new int[2];
        for (int num : nums)
            diff ^= num;
        diff &= -diff;
        for (int num : nums) {
            if ((num & diff) == 0)
                res[0] ^= num;
            else
                res[1] ^= num;
        }
        return res;
    }