Leetcode.88 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 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]

Constraints:

• -10^9 <= nums1[i], nums2[i] <= 10^9
• nums1.length == m + n
• nums2.length == n

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.
        """
        end = m + n - 1
        while m > 0 and n > 0:
            if nums1[m-1] > nums2[n-1]:
                nums1[end] = nums1[m-1]
                end -= 1
                m -= 1
            elif nums1[m-1] < nums2[n-1]:
                nums1[end] = nums2[n-1]
                end -= 1
                n -= 1
            else:
                assert nums1[m-1] == nums2[n-1]
                nums1[end] = nums1[m-1]
                m -= 1
                end -= 1
                nums1[end] = nums2[n-1]
                n -= 1
                end -= 1
        # 不需要判斷m，由於都是存在nums1裡邊的，快排也可以借鑑這個思路
        while n > 0:
            nums1[end] = nums2[n-1]
            end -= 1
            n -= 1