125 lines
3.0 KiB
C#
125 lines
3.0 KiB
C#
var lines = File.ReadAllLines("input.txt");
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var grid = CreateGrid(lines);
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int[][] directions = new int[][]
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{
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[-1, 0],
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[0, -1],
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[0, 1],
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[1, 0]
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};
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var part1 = Part1(grid, directions);
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Console.WriteLine($"Part1: {part1}\n");
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int Part1(char[,] grid, int[][] directions)
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{
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var rows = grid.GetLength(0);
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var columns = grid.GetLength(1);
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var neighbourDictionary = new Dictionary<(int, int), HashSet<(int, int)>>();
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for (var i = 0; i < rows; i++)
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{
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for (int j = 0; j < columns; j++)
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{
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neighbourDictionary[(i, j)] = new HashSet<(int, int)>();
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foreach (var dir in directions)
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{
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var di = dir[0];
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var dj = dir[1];
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if (i + di >= 0 && i + di < rows && j + dj >= 0 && j + dj < columns)
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{
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if (grid[i, j] == grid[i + di, j + dj])
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{
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neighbourDictionary[(i, j)].Add((i + di, j + dj));
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}
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}
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}
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}
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}
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var regions = new List<HashSet<(int, int)>>();
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var remainingPoints = new HashSet<(int, int)>();
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for (var i = 0; i < rows; i++)
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{
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for (var j = 0; j < columns; j++)
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{
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remainingPoints.Add((i, j));
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}
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}
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while (remainingPoints.Count > 0)
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{
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var point = remainingPoints.First();
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remainingPoints.Remove(point);
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var region = GetRegion(point, neighbourDictionary);
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regions.Add(region);
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remainingPoints.ExceptWith(region);
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}
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return regions.Sum(region => Perimeter(region, neighbourDictionary) * region.Count);
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}
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int CountSplitSegments(List<(int, int, int, string)> lines)
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{
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if (lines.Count == 0) return 0;
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var segmentCount = 1;
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for (var i = 1; i < lines.Count; i++)
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{
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var prev = lines[i - 1];
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var curr = lines[i];
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var isContiguous =
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(prev.Item1 == curr.Item1 && curr.Item2 - prev.Item2 == 1 && curr.Item3 == prev.Item3);
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if (!isContiguous)
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{
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segmentCount++;
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}
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}
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return segmentCount;
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}
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HashSet<(int, int)> GetRegion((int, int) point, Dictionary<(int, int), HashSet<(int, int)>> neighbourDict)
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{
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var region = new HashSet<(int, int)>();
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var remaining = new HashSet<(int, int)> { point };
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while (remaining.Count > 0)
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{
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var curPoint = remaining.First();
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remaining.Remove(curPoint);
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region.Add(curPoint);
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var newRemaining = neighbourDict[curPoint].Except(region);
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remaining.UnionWith(newRemaining);
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}
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return region;
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}
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int Perimeter(HashSet<(int, int)> region, Dictionary<(int, int), HashSet<(int, int)>> neighbourDict)
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{
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return region.Sum(point => 4 - neighbourDict[point].Count);
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}
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char[,] CreateGrid(string[] lines)
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{
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var grid = new char[lines.Length, lines[0].Length];
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for (int i = 0; i < lines.Length; i++)
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{
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for (int j = 0; j < lines[i].Length; j++)
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{
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grid[i, j] = lines[i][j];
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}
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}
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return grid;
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} |