Add Day 07 solution

2025-12-07 17:48:20 +01:00
parent 6e3d180550
commit f0ac76df15
2 changed files with 145 additions and 0 deletions
@@ -0,0 +1,98 @@
+using System.Collections.Generic;
+using System.Data.Common;
+using System.IO;
+using System.Linq;
+using AdvenOfCode.Contracts;
+using Coordinate = (int x, int y);
+
+namespace AoC_2025;
+
+public class Day07 : IPuzzleSolver<long>
+{
+    private string[] ParsePuzzleInput(string path)
+    {
+        var puzzleInput = File.ReadAllLines(path)
+            .Where(line => !string.IsNullOrWhiteSpace(line))
+            .ToArray();
+        return puzzleInput;
+    }
+
+    public long SolvePart1(string pathToPuzzleInput)
+    {
+        var grid = ParsePuzzleInput(pathToPuzzleInput);
+        var start = GetStart(grid);
+        var count = TraverseGridAndCountSplitters(grid, start);
+        return count;
+    }
+    
+    public long SolvePart2(string pathToPuzzleInput)
+    {
+        var grid = ParsePuzzleInput(pathToPuzzleInput);
+        var start = GetStart(grid);
+        var count = GetNodesTraversedWitTimelineCount(grid, start, [], []);
+        return count[start];
+    }
+
+    private Coordinate GetStart(string[] grid)
+    {
+        return (0, grid[0].IndexOf('S'));
+    }
+
+    private long TraverseGridAndCountSplitters(string[] grid, Coordinate start)
+    {
+        HashSet<Coordinate> visited = [start];
+        var seen = new Queue<Coordinate>();
+        seen.Enqueue(start);
+        var splittersHit = 0L;
+        while (seen.TryDequeue(out var current))
+        {
+            if (current.x >= grid.Length) continue;
+            if (current.y >= grid[0].Length || current.y < 0) continue;
+
+            if (grid[current.x][current.y] == '^')
+            {
+                splittersHit++;
+                var nextLeft = (current.x, current.y - 1);
+                var nextRight = (current.x, current.y + 1);
+                if (visited.Add(nextLeft)) seen.Enqueue(nextLeft);
+                if (visited.Add(nextRight)) seen.Enqueue(nextRight);
+            }
+            else
+            {
+                var next = (current.x + 1, current.y);
+                if (visited.Add(next)) seen.Enqueue(next);
+            }
+        }
+
+        return splittersHit;
+    }
+    
+    private Dictionary<Coordinate, long> GetNodesTraversedWitTimelineCount(string[] grid, Coordinate current, HashSet<Coordinate> path, Dictionary<Coordinate, long> nodeCountVisited)
+    {
+        if (current.x >= grid.Length || nodeCountVisited.ContainsKey(current))
+        {
+            var addAmount = nodeCountVisited.GetValueOrDefault(current, 1);
+            foreach (var node in path)
+            {
+                nodeCountVisited[node] += addAmount;
+            }
+
+            return nodeCountVisited;
+        }
+
+        nodeCountVisited[current] = 0;
+        path.Add(current);
+
+        if (grid[current.x][current.y] == '^')
+        {
+            var resLeft = GetNodesTraversedWitTimelineCount(grid, (current.x, current.y - 1), [..path], nodeCountVisited);
+            var resRight = GetNodesTraversedWitTimelineCount(grid, (current.x, current.y + 1), [..path], resLeft);
+            return resRight;
+        }
+        else
+        {
+            var res = GetNodesTraversedWitTimelineCount(grid, (current.x + 1, current.y), [..path], nodeCountVisited);
+            return res;
+        }
+    }
+}