136. 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?

思路：

 

使用异或逻辑操作符， 即： a ^ a= 0 , a ^ 0 =a , (a ^ b) ^ c = a ^ (b ^ c) ;

 

 int singleNumber(vector<int>& nums) {
        int val=0;
         for(int num:nums)
            val=val^num;
         return val;
    }