Leetcode 137. 只出现一次的数字 II - 题解

输入: [2,2,3,2]
输出: 3

输入: [0,1,0,1,0,1,99]
输出: 99

     0 -> 1 -> 2 -> 0

     00 -> 01 -> 10 -> 00

     a             b

     0             0

     0 -> 0   0 -> 1

     0 -> 1   1 -> 0

     1 -> 0   0 -> 0

b flip: !a

a flip: !b calculated

return b

public class Solution
{
    public int SingleNumber(int[] nums)
    {
        int a = 0, b = 0;
        for(int i = 0;i < nums.Length;i++)
        {
            b = (b ^ nums[i]) & ~a;
            a = (a ^ nums[i]) & ~b;
        }
        return b;
    }
}