题目描述：
Given an array of integers, every element appears three times except for one. Find that single one.
解题思路：
具体参考Detailed explanation and generalization of the bitwise operation method for single numbers
讲的实在是很全面，而且拓展到了一般的情况，膜！！
代码如下：
public class Solution{
public int singleNumber(int[] nums){
int x1 = 0;
int x2 = 0;
int mask = 0;
for(int i : nums){
x2 ^= x1 & i;
x1 ^= i;
mask = ~(x1 & x2);
x2 &= mask;
x1 &= mask;
}
return x1;
}
}
Java [Leetcode 137]Single Number II
原文：http://www.cnblogs.com/zihaowang/p/5350294.html