LeetCode OJ——Single Number II

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) {
        // Note: The Solution object is instantiated only once and is reused by each test case.
    if(n==1){
        return A[0];
    }
    if(n%3!=1){
		return -1;
	}
	const size_t int_len=8*sizeof(int);
	int tmp[int_len];
	size_t i;
	for(i=0;i<int_len;i++){
		tmp[i]=0;
	}
	int index;
	for(index=0;index<n;index++){
		for(i=0;i<int_len;i++){
			tmp[i]+=(A[index]>>i)&(1);
		}
	}
	int res=0;
	for(i=0;i<int_len;i++){
		if(tmp[i]%3){
			res+=(1)<<(i);
		}
	}
	return res;
    }
};