Merge two sorted arrays in-place

Given two arrays `arr1` and `arr2`, both sorted in **ascending** order. - Modify `arr1` **in-place** to contain all elements from `arr1` and `arr2` in **ascending** order. - **Do not** allocate an additional array for the merge result. Assumptions/clarifications you may use: - `arr1` has enough extra capacity at the end to hold all elements of `arr2` (e.g., `arr1` length is `m + n`, where the first `m` entries are valid and the last `n` are empty slots), and `arr2` has length `n`. - You are given `m` and `n`. Follow-ups: 1. How would you adapt your approach if both arrays were sorted in **descending** order? 2. If the arrays were **not sorted**, what would you do (and what are the time/space trade-offs)? Define the time and space complexity of your approach.