【LeetCode】Single Number

description:

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?

code: ( no extra memory and O(n) runtime complexity)

class Solution {
public:
    int singleNumber(int A[], int n) {
        // Note: The Solution object is instantiated only once and is reused by each test case.
        int res = A[0];
        for(int i = 1; i<n; i++)
        {
            res ^= A[i];
        }
        return res;
    }
};