LeetCode: 88. Merge Sorted Array

The key here is that we need to push elements from nums2 to nums1 while not disturbing the existing elements in nums1.

So, put the elems from nums2 to nums1 from the end.

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.
        """
        p1, p2 = m - 1, n - 1
        for i in range(m+n-1, -1, -1):
            p1_val = nums1[p1] if p1 >= 0 else -float('inf')
            p2_val = nums2[p2] if p2 >= 0 else -float('inf')
            if p1_val >= p2_val:
                nums1[i] = p1_val
                p1 -= 1
            else:
                nums1[i] = p2_val
                p2 -= 1