https://leetcode.cn/problems/single-number-ii/description/
很好的一个解法
class Solution {
public:int singleNumber(vector<int>& nums) {int ones = 0, twos = 0;for (int num : nums) {ones = (ones ^ num) & ~twos;twos = (twos ^ num) & ~ones;}return ones;}
};
题解：https://leetcode.cn/problems/single-number-ii/solutions/2874103/zhuang-tai-ji-mo-3biao-da-shi-de-tui-dao-d2v1/
