AdventOfCode/Days/Day8.cs

using Spectre.Console;

namespace AdventOfCode.Days;

public class Day8 : Day
{
    public override int Number => 8;
    public override string Name => "Treetop Tree House";
    public override void RunPart1(bool display = true)
    {
        var grid = CreateGrid();

        var valid = new HashSet<(int, int)>();

        // Check each line from left to right
        for (int i = 0; i < grid.GetLength(0); i++)
        {
            int previousTreeSize = -1;

            for (int j = 0; j < grid.GetLength(1); j++)
            {
                var size = grid[i, j];

                // The tree on the left is blocking the view, stop searching on this line
                if (size <= previousTreeSize)
                {
                    continue;
                }

                valid.Add((i, j));
                previousTreeSize = size;
            }
        }

        // Check each line from right to left
        for (int i = 0; i < grid.GetLength(0); i++)
        {
            int previousTreeSize = -1;

            for (int j = grid.GetLength(1) - 1; j >= 0; j--)
            {
                var size = grid[i, j];

                // The tree on the left is blocking the view, don't take it
                if (size <= previousTreeSize)
                {
                    continue;
                }

                valid.Add((i, j));
                previousTreeSize = size;
            }
        }

        // Check each column from top to bottom
        for (int j = 0; j < grid.GetLength(1); j++)
        {
            int previousTreeSize = -1;

            for (int i = 0; i < grid.GetLength(0); i++)
            {
                var size = grid[i, j];

                // The tree on the top is blocking the view, stop searching on this column
                if (size <= previousTreeSize)
                {
                    continue;
                }

                valid.Add((i, j));
                previousTreeSize = size;
            }
        }

        // Check each column from bottom to top
        for (int j = 0; j < grid.GetLength(1); j++)
        {
            int previousTreeSize = -1;

            for (int i = grid.GetLength(0) - 1; i >= 0; i--)
            {
                var size = grid[i, j];

                // The tree on bottom is blocking the view, stop searching on this column
                if (size <= previousTreeSize)
                {
                    continue;
                }

                valid.Add((i, j));
                previousTreeSize = size;
            }
        }


        if (display)
        {
            AnsiConsole.MarkupLine($"[green]Total viewable trees: [yellow]{valid.Count}[/][/]");
        }
    }

    public override void RunPart2(bool display = true)
    {
        var grid = CreateGrid();

        var maxScenicScore = 0;

        // Compute scenic score for each tree
        for (int i = 0; i < grid.GetLength(0); i++)
        {
            for (int j = 0; j < grid.GetLength(1); j++)
            {
                var size = grid[i, j];
                var score = ComputeScenicScore(grid, i, j, size);

                if (score > maxScenicScore)
                {
                    maxScenicScore = score;
                }
            }
        }

        if (display)
        {
            AnsiConsole.MarkupLine($"[green]Max scenic score: [yellow]{maxScenicScore}[/][/]");
        }
    }

    private int ComputeScenicScore(int[,] grid, int i, int j, int size)
    {
        var visibleTreeCountLeft = 0;
        var visibleTreeCountRight = 0;
        var visibleTreeCountTop = 0;
        var visibleTreeCountBottom = 0;

        // Look on left
        for (int x = j - 1; x >= 0; x--)
        {
            visibleTreeCountLeft++;
            var nextTreeSize = grid[i, x];

            // Blocking the view
            if (nextTreeSize >= size)
            {
                break;
            }
        }

        // Look on right
        for (int x = j + 1; x < grid.GetLength(1); x++)
        {
            visibleTreeCountRight++;
            var nextTreeSize = grid[i, x];

            // Blocking the view
            if (nextTreeSize >= size)
            {
                break;
            }
        }

        // Look on top
        for (int y = i - 1; y >= 0; y--)
        {
            visibleTreeCountTop++;
            var nextTreeSize = grid[y, j];

            // Blocking the view
            if (nextTreeSize >= size)
            {
                break;
            }
        }

        // Look on bottom
        for (int y = i + 1; y < grid.GetLength(0); y++)
        {
            visibleTreeCountBottom++;
            var nextTreeSize = grid[y, j];

            // Blocking the view
            if (nextTreeSize >= size)
            {
                break;
            }
        }

        return visibleTreeCountLeft * visibleTreeCountRight * visibleTreeCountTop * visibleTreeCountBottom;
    }

    private int[,] CreateGrid()
    {
        var lines = Input.Split('\n').Select(s => s.Trim()).ToArray();

        var grid = new int[lines.Length, lines[0].Length];

        for (int i = 0; i < grid.GetLength(0); i++)
        {
            for (int j = 0; j < grid.GetLength(1); j++)
            {
                grid[i, j] = int.Parse(lines[i][j].ToString());
            }
        }

        return grid;
    }

    #region Input

    public const string Input =
    """
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    """;

    #endregion
}