day 10 part 1

AdventOfCode/Day10.cs

@@ -0,0 +1,96 @@
+namespace AdventOfCode;
+
+public class Day10 : BaseDay
+{
+    int[][] _map;
+
+    public Day10()
+    {
+        string[] lines = File.ReadAllLines(InputFilePath);
+        _map = lines.Select(l => l.Select(x => int.Parse(x.ToString())).ToArray()).ToArray();
+    }
+
+    public override ValueTask<string> Solve_1()
+    {
+        int totalScore = 0;
+        for (int i = 0; i < _map.Length; ++i)
+        {
+            for (int j = 0; j < _map[0].Length; ++j)
+            {
+                if (_map[i][j] == 0)
+                {
+                    totalScore += GetTrailheadScore(i, j);
+                }
+            }
+        }
+
+        return new(totalScore.ToString());
+    }
+
+    public override ValueTask<string> Solve_2()
+    {
+        return new("");
+    }
+
+    private int GetTrailheadScore(int i, int j)
+    {
+        Point start = new Point(i, j);
+        return GetTrailheadScore(start, new HashSet<Point>() { start }, new HashSet<Point>());
+    }
+
+    private int GetTrailheadScore(Point current, HashSet<Point> visited, HashSet<Point> ninePositionsreached)
+    {
+        int currentValue = _map[current.I][current.J];
+        if (currentValue == 9)
+        {
+            if (ninePositionsreached.Add(current))
+            {
+                return 1;
+            }
+            return 0;
+        }
+
+        int score = 0;
+
+        foreach (Point neighbour in GetNeighbourPoints(current))
+        {
+            if (neighbour != null && _map[neighbour.I][neighbour.J] == currentValue + 1)
+            {
+                visited.Add(neighbour);
+                score += GetTrailheadScore(neighbour, visited, ninePositionsreached);
+                visited.Remove(neighbour);
+            }
+        }
+
+        return score;
+    }
+
+    private IEnumerable<Point> GetNeighbourPoints(Point current)
+    {
+        // right
+        if (current.J < _map[0].Length - 1)
+        {
+            yield return new Point(current.I, current.J + 1);
+        }
+
+        // left
+        if (current.J > 0)
+        {
+            yield return new Point(current.I, current.J - 1);
+        }
+
+        // top
+        if (current.I > 0)
+        {
+            yield return new Point(current.I - 1, current.J);
+        }
+
+        // top
+        if (current.I < _map.Length - 1)
+        {
+            yield return new Point(current.I + 1, current.J);
+        }
+    }
+
+    private record Point(int I, int J);
+}