[Adobe] Merge Sorted Array

Problem: 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:

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.

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].

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.

Approach: It's an simple implementatio problem. You can directly go to implementation to understand the approach.

Implementation in C#:

    public void Merge(int[] nums1, int m, int[] nums2, int n)

    {

        int writeIndex = m + n - 1;

        int num1Index = m - 1;

        int num2Index = n - 1;

        while(num1Index >= 0 && num2Index >= 0)

        {

            if (nums1[num1Index] > nums2[num2Index])

            {

                nums1[writeIndex--] = nums1[num1Index--];

            }

            else

            {

                nums1[writeIndex--] = nums2[num2Index--];

            }

        }

        while (num2Index >= 0)

        {

            nums1[writeIndex--] = nums2[num2Index--];

        }

    }

Complexity: O(m + n)