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?

public class Solution {    public int singleNumber(int[] A) {        // Note: The Solution object is instantiated only once and is reused by each test case.         if(A.length == 0)            return 0;        int[] cnt = new int[32];        for(int i = 0; i < A.length; i++)        {            for(int j = 0; j < 32; j++)            {                if( (A[i]>>j & 1) ==1)                {                    cnt[j] = (cnt[j] + 1)%3;                }            }        }        int res = 0;        for(int i = 0; i < 32; i++)        {            res += (cnt[i] << i);        }        cnt = null;        return res;    }}