[2k25] Add day 7

Days/Day7.cs

@@ -0,0 +1,175 @@
+using System.Buffers;
+using System.Numerics;
+using Spectre.Console;
+
+namespace AdventOfCode.Days;
+
+public class Day7 : Day
+{
+    public override int Number => 7;
+    public override string Name => "Laboratories";
+
+    public const int Width = 141;
+    public const int Height = 142;
+
+    public override void RunPart1(bool display = true)
+    {
+        var splitCount = 0;
+
+        var splittersMap = ParseSplittersMap(Input, out var startPosition);
+
+        var beams = new HashSet<Position>();
+        var nextLineBeams = new List<Position>();
+        var usedSplitters = new HashSet<Position>();
+        beams.Add(startPosition with { I = startPosition.I + 1 });
+
+        // Simulate beams going down
+        var row = 1;
+        while (row < Height - 1)
+        {
+            foreach (var beamPosition in beams)
+            {
+                var targetPosition = beamPosition with { I = beamPosition.I + 1 };
+
+                // There is nothing below
+                if (!splittersMap[targetPosition.I, targetPosition.J])
+                {
+                    nextLineBeams.Add(targetPosition);
+                }
+                // There is a splitter, only counts it if not already used
+                else if (usedSplitters.Add(targetPosition))
+                {
+                    splitCount++;
+
+                    // Left and right beam
+                    if (targetPosition.J - 1 >= 0)
+                    {
+                        nextLineBeams.Add(targetPosition with { J = targetPosition.J - 1 });
+                    }
+
+                    if (targetPosition.J + 1 < Width)
+                    {
+                        nextLineBeams.Add(targetPosition with { J = targetPosition.J + 1 });
+                    }
+                }
+            }
+
+            // Always delete current line beams since we iterate from top to bottom
+            beams.Clear();
+            foreach (var nextLineBeam in nextLineBeams)
+            {
+                beams.Add(nextLineBeam);
+            }
+            nextLineBeams.Clear();
+
+            // Also clear the used splitters list for next line
+            usedSplitters.Clear();
+
+            row++;
+        }
+
+        if (display)
+        {
+            AnsiConsole.MarkupLine($"[green]Beam split count: [yellow]{splitCount}[/][/]");
+        }
+    }
+
+    public override void RunPart2(bool display = true)
+    {
+        var splittersMap = ParseSplittersMap(Input, out var startPosition);
+
+        var quantumPositions = new Dictionary<Position, long>();
+        var nextQuantumPositions = new Dictionary<Position, long>();
+        quantumPositions.Add(startPosition with { I = startPosition.I + 1 }, 1L);
+
+        // Simulate beams going down for each timeline
+        var row = 1;
+        while (row < Height - 1)
+        {
+            // Simulation step
+            foreach (var (beamPosition, timelinesCount) in quantumPositions)
+            {
+                var targetPosition = beamPosition with { I = beamPosition.I + 1 };
+
+                // There is nothing below, keep going down
+                if (!splittersMap[targetPosition.I, targetPosition.J])
+                {
+                    UpdateTimelines(nextQuantumPositions, targetPosition, timelinesCount);
+                }
+                else
+                {
+                    // Left and right beams
+                    var leftBeamPosition = targetPosition with { J = targetPosition.J - 1 };
+                    var rightBeamPosition = targetPosition with { J = targetPosition.J + 1 };
+
+                    UpdateTimelines(nextQuantumPositions, leftBeamPosition, timelinesCount);
+                    UpdateTimelines(nextQuantumPositions, rightBeamPosition, timelinesCount);
+                }
+            }
+
+            // Always delete current line beams since we iterate from top to bottom
+            quantumPositions.Clear();
+            foreach (var nextQuantumPosition in nextQuantumPositions)
+            {
+                quantumPositions.Add(nextQuantumPosition.Key, nextQuantumPosition.Value);
+            }
+            nextQuantumPositions.Clear();
+
+            row++;
+        }
+
+        if (display)
+        {
+            AnsiConsole.MarkupLine($"[green]Timelines count: [yellow]{quantumPositions.Sum(p => p.Value)}[/][/]");
+        }
+
+        return;
+
+        // Update and merge timelines
+        static void UpdateTimelines(Dictionary<Position, long> nextQuantumPositions, Position targetPosition, long timelinesCount)
+        {
+            // Merge timelines if there is already one for this target position
+            if (nextQuantumPositions.TryGetValue(targetPosition, out var otherTimelinesCount))
+            {
+                nextQuantumPositions[targetPosition] = otherTimelinesCount + timelinesCount;
+            }
+            // No timelines to merge, no new timeline
+            else
+            {
+                nextQuantumPositions[targetPosition] = timelinesCount;
+            }
+        }
+    }
+
+    private static bool[,] ParseSplittersMap(string input, out Position startPosition)
+    {
+        var map = new bool[Height, Width];
+        startPosition = new Position(0, 0);
+
+        var i = 0;
+        foreach (var line in input.EnumerateLines())
+        {
+            var j = 0;
+            foreach (var symbol in line)
+            {
+                // Find start
+                if (symbol is 'S')
+                {
+                    startPosition = new Position(i, j);
+
+                    continue;
+                }
+
+                map[i, j] = symbol is '^';
+
+                j++;
+            }
+
+            i++;
+        }
+
+        return map;
+    }
+
+    private record Position(int I, int J);
+}