# lc88. Merge Sorted Array

Contents

You are given two integer arrays `nums1` and `nums2`, sorted in non-decreasing order, and two integers `m` and `n`, representing the number of elements in `nums1` and `nums2` respectively.

Merge `nums1` and `nums2` into a single array sorted in non-decreasing order.

The final sorted array should not be returned by the function, but instead be stored inside the array `nums1`. To accommodate this, `nums1` has a length of `m + n`, where the first `m` elements denote the elements that should be merged, and the last `n` elements are set to `0` and should be ignored. `nums2` has a length of `n`.

Example 1:

 ``````1 2 3 4 `````` ``````Input: nums1 = [1,2,3,0,0,0], m = 3, nums2 = [2,5,6], n = 3 Output: [1,2,2,3,5,6] Explanation: The arrays we are merging are [1,2,3] and [2,5,6]. The result of the merge is [1,2,2,3,5,6] with the underlined elements coming from nums1. ``````

Example 2:

 ``````1 2 3 4 `````` ``````Input: nums1 = , m = 1, nums2 = [], n = 0 Output:  Explanation: The arrays we are merging are  and []. The result of the merge is . ``````

Example 3:

 ``````1 2 3 4 5 `````` ``````Input: nums1 = , m = 0, nums2 = , n = 1 Output:  Explanation: The arrays we are merging are [] and . The result of the merge is . Note that because m = 0, there are no elements in nums1. The 0 is only there to ensure the merge result can fit in nums1. ``````

Constraints:

• `nums1.length == m + n`
• `nums2.length == n`
• `0 <= m, n <= 200`
• `1 <= m + n <= 200`
• `-109 <= nums1[i], nums2[j] <= 109`

Follow up: Can you come up with an algorithm that runs in `O(m + n)` time?

##### 思路

 `````` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 `````` ``````class Solution(object): def merge(self, nums1, m, nums2, n): """ :type nums1: List[int] :type m: int :type nums2: List[int] :type n: int :rtype: None Do not return anything, modify nums1 in-place instead. """ insert=-1 m,n=m-1,n-1 while m>=0 and n>=0: if nums1[m]>nums2[n]: nums1[m],nums1[insert]=nums1[insert],nums1[m] m-=1 elif nums1[m]<=nums2[n]: nums1[insert]=nums2[n] n-=1 insert-=1 while n>=0: nums1[insert]=nums2[n] n-=1 insert-=1 ``````