# Merge Sorted Array

> 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.

A和B都已经是排好序的数组,我们只需要从后往前比较就可以了。

因为A有足够的空间容纳A + B,我们使用游标i指向m + n - 1,也就是最大数值存放的地方,从后往前遍历A,B,谁大就放到i这里,同时递减i。

代码如下:

```c++
class Solution {
public:
void merge(int A[], int m, int B[], int n) {
int i = m + n - 1;
int j = m - 1;
int k = n - 1;

while(i >= 0) {
if(j >= 0 && k >= 0) {
if(A[j] > B[k]) {
A[i] = A[j];
j--;
} else {
A[i] = B[k];
k--;
}
} else if(j >= 0) {
A[i] = A[j];
j--;
} else if(k >= 0) {
A[i] = B[k];
k--;
}
i--;
}
}
};
```