Single Number II

class Solution {public:    int singleNumber(int A[], int n) {        const int width=sizeof(int)*8;        int count[width];        memset(count,0,width*sizeof(int));        for(int i=0;i!=n;i++)        {            int flag=1;            for(int j=0;j!=width;j++)            {                if(flag&A[i])   {   count[j]++; }                flag=flag<<1;            }        }        int ret=0;        for(int i=width-1;i>=0;i--)        {            ret=(ret<<1)+(count[i]%3);        }        return ret;    }};