LeetCode Problem : Single Number

Problem 

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

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