Merge 2 Sorted Arrays

Problem Description

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.

Examples

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.

Example 2:

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

Example 3:

• Input: nums1 = [0], m = 0, nums2 = [1], n = 1
• Output: [1]
• Explanation: The arrays we are merging are [] and [1]. The result of the merge is [1]. 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
• -10^9 <= nums1[i], nums2[j] <= 10^9

Follow up

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

Code Template

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.
        """
        # Write your code here

Solutions

• Solution 1: This approach uses a three-pointer technique to merge the two arrays from the end, ensuring that we do not overwrite any elements in nums1 that have not yet been processed. It runs in O(m + n) time and uses O(1) additional space.

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