Merge Sorted Array

From LeetCode

problem description / no solution provided

Solution in Python3

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.
        """
        # Move largest number to the back of nums1.
        p1 = m - 1
        p2 = n - 1
        p = m + n - 1  
        while p1 >= 0 and p2 >= 0:
            if nums1[p1] >= nums2[p2]:
                nums1[p] = nums1[p1]
                p1 -= 1
            else:
                nums1[p] = nums2[p2]
                p2 -= 1
            p -= 1
        while p2 >= 0:
            nums1[p] = nums2[p2]
            p2 -= 1
            p -= 1

I am lucky to get

Runtime: 40 ms, faster than 76.25% of Python3 online submissions for Merge Sorted Array.

Time Complexity

\(O(n + m)\).