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?

C++ Code:

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class Solution {
public:
	int (vector<int>& nums) {
		for(int i = 1; i < nums.size(); ++i) 
			nums[0] ^= nums[i];
		return nums[0];
	}
};