Add day 10

Day10/Program.cs

@@ -0,0 +1,142 @@
+var rawTopographicMap = File.ReadLines("input.txt");
+var topographicMap = CreateTopographicMap(rawTopographicMap);
+
+var availableDirections = new List<(int, int)>()
+{
+    (-1, 0), // Up
+    (1, 0), // Down
+    (0, -1), // Left
+    (0, 1) // Right
+};
+
+Console.WriteLine($"Part1: {Part1(topographicMap, availableDirections)}\nPart2: {Part2(topographicMap, availableDirections)}");
+
+
+int Part2(int[,] mapInput, List<(int, int)> directions)
+{
+    var totalRating = 0;
+    for (var r = 0; r < mapInput.GetLength(0); r++)
+    {
+        for (var c = 0; c < mapInput.GetLength(1); c++)
+        {
+            if (mapInput[r, c] == 0)
+            {
+                totalRating += FindDistinctTrails(r, c, mapInput, directions);
+            }
+        }
+    }
+
+    return totalRating;
+}
+
+int FindDistinctTrails(int r, int c, int[,] mapInput, List<(int, int)> directions)
+{
+    var stack = new Stack<List<(int, int)>>();
+    stack.Push(new List<(int, int)> { (r, c) });
+    var trails = 0;
+
+    while (stack.Count > 0)
+    {
+        var currentPath = stack.Pop();
+        var (cr, cc) = currentPath[^1];
+        
+        if (mapInput[cr, cc] == 9)
+        {
+            trails++;
+            continue;
+        }
+
+        foreach (var (dr, dc) in directions)
+        {
+            var nr = cr + dr;
+            var nc = cc + dc;
+            
+            if (nr >= 0 && nr < mapInput.GetLength(0) && nc >= 0 && nc < mapInput.GetLength(1) &&
+                mapInput[nr, nc] == mapInput[cr, cc] + 1)
+            {
+                var nextPath = new List<(int, int)>(currentPath);
+                nextPath.Add((nr, nc));
+                stack.Push(nextPath);
+            }
+        }
+    }
+
+    return trails;
+}
+
+int Part1(int[,] map, List<(int, int)> directions)
+{
+    var totalScore = 0;
+
+    for (var row = 0; row < map.GetLength(0); row++)
+    {
+        for (var column = 0; column < map.GetLength(1); column++)
+        {
+            if (map[row, column] == 0)
+            {
+                totalScore += TrailHead(row, column, map, directions);
+            }
+        }
+    }
+
+    return totalScore;
+}
+
+int TrailHead(int startRow, int startColumn, int[,] map, List<(int, int)> directions)
+{
+    var rows = map.GetLength(0);
+    var cols = map.GetLength(1);
+    var queue = new Queue<(int, int)>();
+    var visited = new HashSet<(int, int)>();
+    var reachableNines = new HashSet<(int, int)>();
+
+    queue.Enqueue((startRow, startColumn));
+
+    while (queue.Count > 0)
+    {
+        var (r, c) = queue.Dequeue();
+
+        if (visited.Contains((r, c)))
+            continue;
+
+        visited.Add((r, c));
+
+        if (map[r, c] == 9)
+        {
+            reachableNines.Add((r, c));
+            continue;
+        }
+
+        foreach (var dir in directions)
+        {
+            var nr = r + dir.Item1;
+            var nc = c + dir.Item2;
+
+            if (nr >= 0 && nr < rows && nc >= 0 && nc < cols)
+            {
+                if (map[nr, nc] == map[r, c] + 1)
+                {
+                    queue.Enqueue((nr, nc));
+                }
+            }
+        }
+    }
+
+    return reachableNines.Count;
+}
+
+int[,] CreateTopographicMap(IEnumerable<string> lines)
+{
+    var lineList = lines.Select(line => line.Trim()).ToList();
+    var map = new int[lineList.Count, lineList[0].Length];
+
+    for (var r = 0; r < map.GetLength(0); r++)
+    {
+        for (var c = 0; c < map.GetLength(1); c++)
+        {
+            map[r, c] = lineList[r][c] - '0';
+        }
+    }
+
+    return map;
+}