class Solution {
public:
    void merge(int A[], int m, int B[], int n) {
        int a = m-1;
        int b = n-1;
        int right = m + n - 1;
        while(a>=0 && b>=0)
        {
            if(A[a] >= B[b])
            {
                A[right] = A[a];
                a--;
            }
            else {
                A[right] = B[b];
                b--;
            }
            right--;
        }
        while(b>=0)
        {
            A[right] = B[b];
            b--;
            right--;
        }
    }
};

解题思路:双指针