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Problem

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:

**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.

Solve

Allocating new memory

O(n)

This is the foundation of merge sort 

class Solution:
    def merge(self, nums1: List[int], m: int, nums2: List[int], n: int) -> None:
        """
        Do not return anything, modify nums1 in-place instead.
        """
        result = nums1
        nums1 = nums1[:m].copy()
        p1 = 0
        p2 = 0
        for i in range(m+n):
            if p1 >= len(nums1):
                result[i] = nums2[p2]
                p2 += 1
            elif p2 >= len(nums2):
                result[i] = nums1[p1]
                p1 += 1
            elif nums1[p1] < nums2[p2]:
                result[i] = nums1[p1]
                p1 += 1
            else:
                result[i] = nums2[p2]
                p2 += 1
Last update : September 17, 2023
Created : August 17, 2023