LeetCode 88. Merge Sorted Array

Description

https://leetcode.com/problems/merge-sorted-array/

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]

Explanation

The straightforward implementation would be to set get one pointer in the beginning of nums1, another pointer at the beginning of nums2, and push the smallest value in the output array at each step.

Python Solution

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.
        """
        if not nums1:
            return nums2
        
        if not nums2:
            return nums1
        
        i = 0
        j = 0
        
        result = []
        
        while i < m and j < n:
            if nums1[i] < nums2[j]:
                result.append(nums1[i])
                i += 1
            else:
                result.append(nums2[j])
                j += 1

        while i < m:
            result.append(nums1[i])
            i += 1            
            
        while j < n:
            result.append(nums2[j])
            j += 1

        for k in range(m + n):
            nums1[k] = result[k]
  • Time complexity: O(m + n).
  • Space complexity: O(m + n).

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