102 lines
3.3 KiB
C#
102 lines
3.3 KiB
C#
using System.Collections.Generic;
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using System.Data.Common;
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using System.IO;
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using System.Linq;
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using AdvenOfCode.Contracts;
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using Coordinate = (int x, int y);
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namespace AoC_2025;
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public class Day07 : IPuzzleSolver<long>
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{
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private string[] ParsePuzzleInput(string path)
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{
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var puzzleInput = File.ReadAllLines(path)
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.Where(line => !string.IsNullOrWhiteSpace(line))
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.ToArray();
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return puzzleInput;
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}
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public long SolvePart1(string pathToPuzzleInput)
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{
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var grid = ParsePuzzleInput(pathToPuzzleInput);
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var start = GetStart(grid);
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var count = TraverseGridAndCountSplitters(grid, start);
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return count;
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}
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public long SolvePart2(string pathToPuzzleInput)
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{
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var grid = ParsePuzzleInput(pathToPuzzleInput);
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var start = GetStart(grid);
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var count = GetNodesTraversedWitTimelineCount(grid, start, [], []);
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return count[start];
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}
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private Coordinate GetStart(string[] grid)
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{
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return (0, grid[0].IndexOf('S'));
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}
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private long TraverseGridAndCountSplitters(string[] grid, Coordinate start)
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{
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HashSet<Coordinate> visited = [start];
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var seen = new Queue<Coordinate>();
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seen.Enqueue(start);
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var splittersHit = 0L;
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while (seen.TryDequeue(out var current))
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{
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if (current.x >= grid.Length) continue;
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if (current.y >= grid[0].Length || current.y < 0) continue;
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if (grid[current.x][current.y] == '^')
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{
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splittersHit++;
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var nextLeft = (current.x, current.y - 1);
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var nextRight = (current.x, current.y + 1);
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if (visited.Add(nextLeft)) seen.Enqueue(nextLeft);
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if (visited.Add(nextRight)) seen.Enqueue(nextRight);
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}
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else
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{
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var next = (current.x + 1, current.y);
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if (visited.Add(next)) seen.Enqueue(next);
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}
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}
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return splittersHit;
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}
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private Dictionary<Coordinate, long> GetNodesTraversedWitTimelineCount(string[] grid, Coordinate current, HashSet<Coordinate> path, Dictionary<Coordinate, long> nodeCountVisited)
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{
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if (current.x >= grid.Length || nodeCountVisited.ContainsKey(current))
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{
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nodeCountVisited = UpdateNodeVisitedCounts(current, path, nodeCountVisited);
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return nodeCountVisited;
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}
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nodeCountVisited[current] = 0;
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path.Add(current);
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if (grid[current.x][current.y] == '^')
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{
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var resLeft = GetNodesTraversedWitTimelineCount(grid, (current.x, current.y - 1), [..path], nodeCountVisited);
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var resRight = GetNodesTraversedWitTimelineCount(grid, (current.x, current.y + 1), [..path], resLeft);
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return resRight;
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}
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var res = GetNodesTraversedWitTimelineCount(grid, (current.x + 1, current.y), [..path], nodeCountVisited);
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return res;
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}
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private static Dictionary<Coordinate, long> UpdateNodeVisitedCounts(Coordinate current, HashSet<Coordinate> path, Dictionary<Coordinate, long> nodeCountVisited)
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{
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var addAmount = nodeCountVisited.GetValueOrDefault(current, 1);
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foreach (var node in path)
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{
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nodeCountVisited[node] += addAmount;
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}
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return nodeCountVisited;
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}
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} |