122 lines
4.0 KiB
C#
122 lines
4.0 KiB
C#
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namespace day3;
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public class Day3
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{
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private int _rows;
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private int _columns;
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private char[][] _grid;
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public Day3(string fileContents)
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{
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var lines = fileContents.Split(Environment.NewLine);
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_grid = lines.Select(line => line.ToCharArray()).ToArray();
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_rows = _grid.Length;
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_columns = _grid[0].Length;
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}
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private bool _isCharacterASymbol(char c) {
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return !char.IsDigit(c) && c != '.';
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}
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private bool _isSymbolInSurroundingLocation(int i, int j)
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{
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var foundSymbol = false;
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for (var ii = i - 1; ii <= i + 1; ii++)
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{
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for (var jj = j - 1; jj <= j + 1; jj++)
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{
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if (ii >= 0 && jj >= 0 && ii < _rows && jj < _columns) {
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foundSymbol |= _isCharacterASymbol(_grid[ii][jj]);
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}
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}
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}
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return foundSymbol;
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}
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private IEnumerable<MachinePart> _getSurroundingMachineParts(int i, int j, IList<MachinePart> machineParts)
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{
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return machineParts.Where(machinePart => machinePart.Locations.Aggregate(false, (hasBeenFound, currentPoint) => {
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var differenceRow = Math.Abs(i - currentPoint.Item1);
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var differenceCol = Math.Abs(j - currentPoint.Item2);
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return hasBeenFound || (!(differenceRow == 0 && differenceCol == 0) && differenceRow <= 1 && differenceCol <= 1);
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}));
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}
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private IList<MachinePart> _getAllMachinePartsInGrid()
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{
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var machinePartsList = new List<MachinePart>();
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int currentlyParsedNumber = 0;
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var locations = new List<(int, int)>();
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bool isSymbolFound = false;
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// We want to iterate over every cell
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for (int 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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var cellContents = _grid[i][j];
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if (char.IsDigit(cellContents))
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{
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// Check the surroundings for a symbol
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isSymbolFound |= _isSymbolInSurroundingLocation(i, j);
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locations.Add((i, j));
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currentlyParsedNumber = (currentlyParsedNumber * 10) + int.Parse(cellContents.ToString());
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}
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// Check if we are done scanning the number (i.e. at the end of a row or we find a non-integer)
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if (!char.IsDigit(cellContents) || j == _columns - 1)
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{
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if (isSymbolFound)
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{
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machinePartsList.Add(new MachinePart {
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Id = machinePartsList.Count,
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Value = currentlyParsedNumber,
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Locations = locations
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});
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}
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locations = new List<(int, int)>();
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currentlyParsedNumber = 0;
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isSymbolFound = false;
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}
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}
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}
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return machinePartsList;
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}
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public int PartOne()
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{
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var machinePartsList = _getAllMachinePartsInGrid();
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return machinePartsList.Aggregate(0, (total, current) => total + current.Value);
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}
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public long PartTwo()
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{
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var machinePartsList = _getAllMachinePartsInGrid();
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var runningTotal = 0L;
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// We are going to do a scan for all gears
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for (int 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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var cellContents = _grid[i][j];
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if (cellContents == '*')
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{
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var surroundingMachineParts = _getSurroundingMachineParts(i, j, machinePartsList);
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var numberOfSurroundingMachingParts = surroundingMachineParts.Count();
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if (numberOfSurroundingMachingParts == 2) {
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runningTotal += surroundingMachineParts.Aggregate(1, (currentRatio, machinePart) => currentRatio * machinePart.Value);
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}
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}
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}
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}
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return runningTotal;
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}
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}
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