Leetcode::Single Number

思想：相同数异或运算等于0；

class Solution {
public:
    int singleNumber(int A[], int n) {
        // IMPORTANT: Please reset any member data you declared, as
        // the same Solution instance will be reused for each test case.
        int sum = A[0];
        for( int i = 1; i < n; i++ )
        {
            sum ^= A[i];    
        }
        
        return sum;
    }
};