【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：

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

       //B中还有元素，继续处理
        while(j >= 0)
        {
            A[end] = B[j];
            j--;
            end--;
        }
    }
};