【LeetCode程序员面试金典】面试题 10.01. Sorted Merge LCCI

You are given two sorted arrays, A and B, where A has a large enough buffer at the end to hold B. Write a method to merge B into A in sorted order.

Initially the number of elements in A and B are m and n respectively.

Example:

Input: A = [1,2,3,0,0,0], m = 3 B = [2,5,6], n = 3

Output: [1,2,2,3,5,6]

来源：力扣（LeetCode） 链接：https://leetcode-cn.com/problems/sorted-merge-lcci 著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。

双指针

A的后面是空的，所以可以换一个思路，从最后一个值开始判断最大值存入

从后往前遍历，就不会被内存空间所限制

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