Merge Two Sorted Arrays In Place

Question

## Problem

Merge `nums2` into `nums1` (which has trailing space) in place so the result is sorted.

## Example
```
nums1=[1,2,3,0,0,0] m=3, nums2=[2,5,6] n=3 -> [1,2,2,3,5,6]
```

## Constraints
- 0 ≤ m,n ≤ 200

## Approach
Merge from the back to avoid overwrites. O(m+n).