First, clarify the problem constraints and expected output format, then outline a simple algorithm that determines the maximum height, iterates from top to bottom, and prints each row with '+' for columns at or above the current level and spaces otherwise. Finally, discuss edge cases and potential optimizations.
Pro tip: Before coding, walk through a small example (e.g., [3,1,2]) to confirm the row-by-row approach and demonstrate your ability to verify logic early. Also, mention that you'd handle empty arrays or all-zero heights gracefully.
Ask about input size, whether heights can be negative or zero, and if the base layer is always printed. Confirm the exact ASCII format (e.g., spaces for empty cells, no trailing spaces).
Find the maximum height to determine the number of rows. For each row from maxHeight down to 1, iterate through the array and print '+' if the column height is >= current row, else print a space. After the loop, print the base layer.
Write clean code with meaningful variable names. Test with simple cases like [1,2,3], [0,0,0], and an empty array to ensure correctness.
State that time complexity is O(n * maxHeight) and space is O(1) extra. Mention that if maxHeight is huge, you could optimize by only iterating up to the maximum height, but that's inherent.
Address empty input, all zeros, and negative heights (if allowed). Ensure the base layer is printed correctly and no extra spaces are added.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.
Clarify the problem constraints and assumptions, then propose a simulation approach where each water unit is poured and moved to the lowest reachable position using a search or iterative settling. Discuss trade-offs between different algorithms (e.g., BFS/DFS vs. union-find) and handle tie-breaking by preferring left. Finally, outline how to update and print the terrain.
Pro tip: Demonstrate awareness of edge cases like water overflowing boundaries or getting trapped in local minima, and mention that the tie-breaking rule (left first) can be implemented by checking left neighbor before right. Also, consider using a priority queue to efficiently find the lowest reachable cell if the terrain is large.
Ask questions to confirm assumptions: Is the terrain a 1D array? Can water flow infinitely? What if water cannot settle (e.g., at edges)? Confirm that each unit of water is placed sequentially and settles before the next.
Decide how to represent the terrain and water. For example, use an array of heights and a separate array for water counts, or modify the terrain to include water levels. Consider if water can stack.
For each water unit, simulate flow: from the starting column, repeatedly move to the lowest reachable neighbor (left first on ties) until no lower neighbor exists. Use BFS/DFS or iterative approach. Consider using a visited set to avoid cycles.
Ensure that when neighbors have equal height, the left neighbor is chosen. Also, define behavior at boundaries: water cannot flow outside the terrain, so it settles at the edge if no lower neighbor.
Write code to pour all water units, then output the terrain with 'W' for water cells. Test with small cases, including flat terrain, slopes, and basins.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.