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 andn respectively.

题目解析：

将A和B两个数组合并到A中，A中有足够的空间。我们可以利用从后向前比较，来移动，就不需要额外申请空间了。这道题目跟《面试题4替换空格》相似，都是从后向前去遍历。

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