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?

class Solution {public:    int singleNumber(int A[], int n) {        int bitcount=sizeof(int) * 8;         int record[bitcount];        memset(record,0,bitcount*sizeof(int));        int mask;        for(int i=0;i<n;++i)           for(int j=0;j<bitcount;++j)           {                record[j]+=A[i]>>j&1;           }        int result=0;        for(int i=0;i<bitcount;++i)            result|=(record[i]%3)<<i;        return result;    }};

模拟三进制