Solve array merge, tree view, and maze tasks

Solve the following coding tasks.

1) Merge two sorted arrays in-place

You are given two integer arrays A and B, each sorted in non-decreasing order.

• A has length m + n , where the first m elements are valid, and the last n elements are extra space.
• B has length n .

Task: Modify A in-place so that it becomes a single sorted array containing all m + n elements.

Constraints (typical): 0 ≤ m, n ≤ 2e5, values fit in 32-bit signed int.

2) Right-side view of a binary tree (variant)

Given the root of a binary tree, return the list of node values visible when looking at the tree from the right side (i.e., the last node encountered at each depth when scanning left-to-right).

Task: Output the values from top to bottom.

Constraints (typical): up to 2e5 nodes.

3) Maze problem (multi-part)

You are given a 2D grid representing a maze:

• '.' = empty cell, '#' = wall
• 'S' = start, 'E' = end
• You can move in 4 directions (up/down/left/right) to non-wall cells.

Tasks: A. Determine whether a path exists from S to E. B. If a path exists, return the length of the shortest path (number of moves). C. Optionally, return one shortest path as a string over {U,D,L,R}.

Constraints (typical): grid size up to 2000 x 2000 (so algorithms should be near-linear in number of cells).