Single Number

Q: 求出数组中只出现1次的数，其他数都出现2次。

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