[2022] Day 12 added
--> Solution is slow as hell --> Could probably use new algorithm
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* [Day 6](https://github.com/TiagoRG/AdventOfCode/tree/main/AdventOfCode/Year2022/Day6.cs)
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* [Day 7](https://github.com/TiagoRG/AdventOfCode/tree/main/AdventOfCode/Year2022/Day7.cs)
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* [Day 8](https://github.com/TiagoRG/AdventOfCode/tree/main/AdventOfCode/Year2022/Day8.cs)
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* [Day 9](https://github.com/TiagoRG/AdventOfCode/tree/main/AdventOfCode/Year2022/Day9.cs)
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* [Day 9](https://github.com/TiagoRG/AdventOfCode/tree/main/AdventOfCode/Year2022/Day9.cs)
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* [Day 10](https://github.com/TiagoRG/AdventOfCode/tree/main/AdventOfCode/Year2022/Day10.cs)
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* [Day 11](https://github.com/TiagoRG/AdventOfCode/tree/main/AdventOfCode/Year2022/Day11.cs)
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* [Day 12](https://github.com/TiagoRG/AdventOfCode/tree/main/AdventOfCode/Year2022/Day12.cs)
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namespace AdventOfCode.Year2022;
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public class Day12
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{
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private const int SOrd = -14;
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private const int EOrd = -28;
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private static short[,]? _map;
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private static (int, int) _sCoords;
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private static (int, int) _eCoords;
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/// <summary>
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/// Slowest solution so far.
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/// Could most certainly use some improvements :skull:
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/// </summary>
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public Day12()
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{
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Console.WriteLine($@"
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Day12 Solution
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Part1 Result: {Part1()}
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Part2 Result: {Part2()}
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=============================");
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}
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private static void PartInit()
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{
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var lines = File.ReadAllLines("inputs/day12.txt");
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var map = new short[lines.Length, lines[0].Length];
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for (var i = 0; i < lines.Length; i++)
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for (var j = 0; j < lines[i].Length; j++)
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map[i, j] = (short)(Convert.ToInt16(lines[i][j]) - 97);
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_map = map;
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_sCoords = FindCoords(map, SOrd);
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_eCoords = FindCoords(map, EOrd);
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}
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private static int Part1()
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{
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PartInit();
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var distances = GetIndexes(_map!).Where(item => item != _sCoords)
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.ToDictionary(index => (index.Item1, index.Item2), _ => short.MaxValue);
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distances[(_sCoords.Item1, _sCoords.Item2)] = 0;
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_map![_sCoords.Item1, _sCoords.Item2] = 0;
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_map[_eCoords.Item1, _eCoords.Item2] = (short)(Convert.ToInt16('z') - 97);
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var visited = new List<(int, int)>();
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var current = _sCoords;
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var unvisited = GetIndexes(_map).ToList();
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while (true)
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try
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{
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Dijkstra(current, distances, visited, Part.Part1);
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unvisited.Remove(current);
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current = distances.Where(pair => unvisited.Contains(pair.Key)).MinBy(pair => pair.Value).Key;
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}
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catch (InvalidOperationException)
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{
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return distances[_eCoords];
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}
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}
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private static int Part2()
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{
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PartInit();
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var distances = GetIndexes(_map!).ToDictionary(index => (index.Item1, index.Item2), _ => short.MaxValue);
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distances[(_eCoords.Item1, _eCoords.Item2)] = 0;
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_map![_sCoords.Item1, _sCoords.Item2] = 0;
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_map[_eCoords.Item1, _eCoords.Item2] = (short)(Convert.ToInt16('z') - 97);
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var visited = new List<(int, int)>();
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var current = _eCoords;
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var unvisited = GetIndexes(_map).ToList();
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var aIndexes = FindAllCoords(_map, 0).ToList();
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while (true)
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{
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if (aIndexes.Contains(Dijkstra(current, distances, visited, Part.Part2)))
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return distances.Where(pair => aIndexes.Contains(pair.Key)).Min(pair => pair.Value);
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unvisited.Remove(current);
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current = distances.Where(pair => unvisited.Contains(pair.Key)).MinBy(pair => pair.Value).Key;
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}
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}
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private static (int, int) Dijkstra((int, int) current, IDictionary<(int, int), short> distances,
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ICollection<(int, int)> visited, Part part)
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{
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var nextCoords = new Dictionary<char, (int, int)>
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{
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['D'] = (current.Item1 + 1, current.Item2),
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['U'] = (current.Item1 - 1, current.Item2),
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['R'] = (current.Item1, current.Item2 + 1),
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['L'] = (current.Item1, current.Item2 - 1)
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};
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if (current.Item1 < _map!.GetLength(0) - 1
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&& IsStepPossible(current, nextCoords['D'], part)
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&& !visited.Contains(nextCoords['D']))
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UpdateDistances(distances, current, nextCoords['D']);
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if (current.Item1 > 0
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&& IsStepPossible(current, nextCoords['U'], part)
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&& !visited.Contains(nextCoords['U']))
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UpdateDistances(distances, current, nextCoords['U']);
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if (current.Item2 < _map.GetLength(1) - 1
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&& IsStepPossible(current, nextCoords['R'], part)
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&& !visited.Contains(nextCoords['R']))
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UpdateDistances(distances, current, nextCoords['R']);
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if (current.Item2 > 0
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&& IsStepPossible(current, nextCoords['L'], part)
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&& !visited.Contains(nextCoords['L']))
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UpdateDistances(distances, current, nextCoords['L']);
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visited.Add(current);
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return current;
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}
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private static bool IsStepPossible((int, int) currentCoords, (int, int) nextCoord, Part part)
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{
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return part switch
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{
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Part.Part1 => _map![nextCoord.Item1, nextCoord.Item2] - 1 <= _map[currentCoords.Item1, currentCoords.Item2],
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Part.Part2 => _map![nextCoord.Item1, nextCoord.Item2] + 1 >= _map[currentCoords.Item1, currentCoords.Item2],
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_ => throw new ArgumentOutOfRangeException(nameof(part), part, null)
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};
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}
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private static void UpdateDistances(IDictionary<(int, int), short> distances, (int, int) currentCoords,
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(int, int) nextCoords)
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{
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if (distances[(nextCoords.Item1, nextCoords.Item2)] == short.MaxValue ||
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distances[(nextCoords.Item1, nextCoords.Item2)] > distances[(currentCoords.Item1, currentCoords.Item2)])
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distances[(nextCoords.Item1, nextCoords.Item2)] =
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(short)(distances[(currentCoords.Item1, currentCoords.Item2)] + 1);
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}
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/// <summary>
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/// Finds the first occurrence of a value in a 2D array
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/// </summary>
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/// <param name="array">The 2D array</param>
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/// <param name="value">The value to be found</param>
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/// <returns></returns>
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/// <exception cref="ArgumentNullException">Array can't be null</exception>
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private static (int, int) FindCoords(short[,] array, int value)
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{
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if (array == null) throw new ArgumentNullException(nameof(array));
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foreach (var index in GetIndexes(array))
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if (array[index.Item1, index.Item2] == value)
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return (index.Item1, index.Item2);
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return (-1, -1);
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}
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/// <summary>
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/// Finds all coordinates of a value in a 2D array
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/// </summary>
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/// <param name="array">The 2D array</param>
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/// <param name="value">The value to be found</param>
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/// <returns></returns>
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/// <exception cref="ArgumentNullException">Array can't be null</exception>
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private static IEnumerable<(int, int)> FindAllCoords(short[,] array, int value)
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{
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if (array == null) throw new ArgumentNullException(nameof(array));
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return from index in GetIndexes(array)
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where array[index.Item1, index.Item2] == value
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select (index.Item1, index.Item2);
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}
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/// <summary>
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/// Returns an enumerable of all indexes of a 2D array
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/// </summary>
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/// <param name="array">The 2D array</param>
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/// <returns></returns>
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/// <exception cref="ArgumentNullException">Array can't be null</exception>
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private static IEnumerable<(int, int)> GetIndexes(short[,] array)
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{
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if (array == null) throw new ArgumentNullException(nameof(array));
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for (var i = 0; i < array.GetLength(0); i++)
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for (var j = 0; j < array.GetLength(1); j++)
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yield return (i, j);
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}
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private enum Part
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{
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Part1,
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Part2
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}
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}
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