88. Merge Sorted Array

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.

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
• -109 <= nums1[i], nums2[j] <= 109

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

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.
        """
        l = r = i = 0
        tempnums1 = nums1[::]

        while l < m and r < n:
            if tempnums1[l] <= nums2[r]:
                nums1[i] = tempnums1[l]
                l += 1
            elif tempnums1[l] > nums2[r]:
                nums1[i] = nums2[r]
                r += 1
            i += 1

        while l < m:
            nums1[i] = tempnums1[l]
            l += 1
            i += 1

        while r < n:
            nums1[i] = nums2[r]
            r += 1
            i += 1

class Solution {
    public void merge(int[] nums1, int m, int[] nums2, int n) {
        int l = m - 1;
        int r = n - 1;
        int i = m + n - 1;

        while (r >= 0) {
            if (l >= 0 && nums1[l] > nums2[r]) {
                nums1[i--] = nums1[l--];
            } else {
                nums1[i--] = nums2[r--];
            }
        }


    }
}