Uploading Days 1-3

day3/Day3.cs

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

day3/MachinePart.cs

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+namespace day3;
+
+public class MachinePart
+{
+    public int Id { get; set; }
+    public int Value { get; set; }
+
+    public IList<(int, int)> Locations { get; set; } = new List<(int, int)>();
+
+}

day3/Program.cs

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+using day3;
+
+var fileContents = File.ReadAllText(Path.GetFullPath("input.txt"));
+var day3 = new Day3(fileContents);
+Console.WriteLine($"The answer to Part 1 is {day3.PartOne()}");
+Console.WriteLine($"The answer to Part 2 is {day3.PartTwo()}");
+Console.WriteLine("Hello World");

day3/day3.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net7.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+</Project>