Given two sorted integer arrays A and B, merge B into A as one sorted array.

Note:
You may assume that A has enough space (size that is greater or equal to m + n) to hold additional elements from B. The number of elements initialized in A and B are m and n respectively.

插入一个新元素会导致插入位置后面的所有元素的移动，为避免大量的移动，通常的办法就是从后面到前面插入，即反向插入和移动元素

    void merge(int A[], int m, int B[], int n) {        int indexA = m-1, indexB = n-1, index = m+n-1;        while(indexB>=0 && indexA >=0 ){            if(B[indexB] > A[indexA]) A[index--] = B[indexB--];            else A[index--] = A[indexA--];        }        while(indexB>=0) A[index--] = B[indexB--];    }