Given two sorted integer arrays nums1 and nums2, merge nums2 into nums1 as one sorted array.

Note:

The number of elements initialized in nums1 and nums2 are m and n respectively.
You may assume that nums1 has enough space (size that is greater or equal to m + n) to hold additional elements from nums2.
Example:

Input:
nums1 = [1,2,3,0,0,0], m = 3
nums2 = [2,5,6], n = 3

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

Solution

Time Complexity O(N)
Space O(1)
倒序插入即可避免shift等的操作

class Solution {
    public void merge(int[] nums1, int m, int[] nums2, int n) {
        int idxM=m-1;
        int idxN=n-1;
        for(int i=m+n-1;i>=0;i--){
            if(idxM<0){
                nums1[i]=nums2[idxN--];
            }
            else if(idxN<0){
                nums1[i]=nums1[idxM--];
            }
            else if( nums1[idxM]>nums2[idxN]){
                nums1[i]=nums1[idxM--];
                
            }
            else
                nums1[i]=nums2[idxN--];
        }
    }
}