LeetCode:Single Number

Given an array of integers, every element appears twice except for one. Find that single one.

Note:
Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory?

这题首先看到要求线性时间复杂度，觉得排序肯定没戏，后来自己折腾还是先用的排序，果然超时。最后参考了别人的代码，是用位运算解决的。没用过位运算，翻了《C Primer Plus》第15章位操作，恶补。

class Solution{
public:
    int singleNumber(int A[],int n){
        int i,bit=0;
        if(n<0)
        {
            return -1;
        }
        for(i=0;i<n;i++)
        {
            bit^=A[i];
        }
        return bit;
    }
};