leetcode - Single Number II

Given an array of integers, every element appears three times except for one. Find that single one.

Note:

Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory?

分析：没想出来，网上看到的算法，用二进制模拟三进制，非常巧妙

class Solution {
public:
int singleNumber(int A[], int n) {
int one = 0;
int two = 0;
int three = 0;

for(int i = 0; i < n; i++)
{
two =two|(one&A[i]);
one ^= A[i];
three = one&two;
one = ~three&one;
two = ~three&two;
}

return one;
}
};