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?
利用异或的性质：
1 class Solution { 2 public: 3 int singleNumber(vector<int>& nums) 4 { 5 int n = nums.size(); 6 int res = 0; 7 for (int i = 0; i < n; ++i) 8 { 9 res ^= nums[i]; 10 } 11 return res; 12 } 13 };