LeetCode-Single Number II

public class  {
    public int singleNumber(int[] A) {
        int ret=0,index=0;
        int[] binarySum=new int[32];
        if(A==null || A.length==0)
            return ret;
        
        for(int i=0;i<A.length;i++)
        {
            index=0;
            do
            {
                binarySum[index++]+=A[i]%2;
                A[i]/=2;
            }while(A[i]!=0);
        }
        
        
        for(int i=0;i<binarySum.length;i++)
        {
            index=binarySum[i]%3;
            if(Math.abs(index)>1)
            {
                index=(index+3)%3;
            }
            ret+=Math.pow(2, i)*(index);
        }
        
        return ret;
    }
}