【leetcode】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 andn respectively.

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题解：查了资料才想到要从后往前合并。把end初始化为m+n-1，即A在合并后最后一个元素的位置。然后把A和B从后往前比较，较大的元素放在end所指的地方。最后要特别注意B的处理，如果A的元素遍历完了，但是B中的元素还没有全部放到A中去，要再用一个while循环单独处理B。

代码如下：

 1 class Solution {

 2 public:

 3     void merge(int A[], int m, int B[], int n) {

 4         int end = m+n-1;

 5         int i,j;

 6         for(i = m-1,j =n-1;i>=0 && j>=0;){

 7             if(A[i] > B[j]){

 8                 A[end] = A[i];

 9                 i--;

10             }

11             else{

12                 A[end] = B[j];

13                 j--;

14             }

15             end --;

16         }

17 

18        //B中还有元素，继续处理

19         while(j >= 0)

20         {

21             A[end] = B[j];

22             j--;

23             end--;

24         }

25     }

26 };