Day 13

advent-of-code-2023.csproj

@@ -54,6 +54,8 @@
 	  <EmbeddedResource Include="inputs\10a.txt" />
 	  <EmbeddedResource Include="inputs\11.txt" />
 	  <EmbeddedResource Include="inputs\11a.txt" />
+	  <EmbeddedResource Include="inputs\13.txt" />
+	  <EmbeddedResource Include="inputs\13a.txt" />
 	</ItemGroup>
 
 	<ItemGroup>

inputs/13a.txt

@@ -0,0 +1,15 @@
+#.##..##.
+..#.##.#.
+##......#
+##......#
+..#.##.#.
+..##..##.
+#.#.##.#.
+
+#...##..#
+#....#..#
+..##..###
+#####.##.
+#####.##.
+..##..###
+#....#..#

src/13.cs

@@ -0,0 +1,134 @@
+using aoc2023.Util;
+
+namespace aoc2023;
+
+internal class Day13 : Day
+{
+    private int part1;
+    private int part2;
+    internal override void Parse()
+    {
+        var lines = Parsing.ReadAllLines($"{GetDay()}");
+
+        List<string> grid = new();
+        void ProcessGrid()
+        {
+            (int res1, int res2) = CheckGrid(grid);
+            part1 += res1;
+            part2 += res2;
+        }
+
+        foreach (var line in lines)
+        {
+            if (line.Length == 0)
+            {
+                ProcessGrid();
+                grid.Clear();
+            }
+            else
+            {
+                grid.Add(line);
+            }
+        }
+
+        ProcessGrid();
+    }
+
+    (int, int) CheckColumns(IList<string> grid)
+    {
+        int part1Columns = 0;
+        int part2Columns = 0;
+
+        for (int checkCol = 1; checkCol < grid[0].Length; checkCol++)
+        {
+            int columnSpread = System.Math.Min(checkCol, grid[0].Length - checkCol);
+            int leftCol = checkCol - 1;
+            int rightCol = checkCol;
+
+            int matches = 0;
+
+            for (int dx = 0; dx < columnSpread; dx++)
+            {
+                int leftMatch = leftCol - dx;
+                int rightMatch = rightCol + dx;
+                matches += grid.Count(l => l[leftMatch] == l[rightMatch]);
+            }
+
+            int maxCount = columnSpread * grid.Count;
+            if (matches == maxCount)
+            {
+                part1Columns = checkCol;
+            }
+            else if (matches == maxCount - 1)
+            {
+                part2Columns = checkCol;
+            }
+        }
+
+        return (part1Columns, part2Columns);
+    }
+
+    (int, int) CheckRows(IList<string> grid)
+    {
+        int part1Rows = 0;
+        int part2Rows = 0;
+
+        for (int checkRow = 1; checkRow < grid.Count; checkRow++)
+        {
+            int rowSpread = System.Math.Min(checkRow, grid.Count - checkRow);
+            int upRow = checkRow - 1;
+            int downRow = checkRow;
+
+            int matches = 0;
+
+            for (int dy = 0; dy < rowSpread; dy++)
+            {
+                int upMatch = upRow - dy;
+                int downMatch = downRow + dy;
+
+                string lineUp = grid[upMatch];
+                string lineDown = grid[downMatch];
+
+                for (int i = 0; i < lineUp.Length; i++)
+                {
+                    int c1 = lineUp[i];
+                    int c2 = lineDown[i];
+                    if (c1 == c2)
+                    {
+                        matches++;
+                    }
+                }
+            }
+
+            int maxCount = rowSpread * grid[0].Length;
+            if (matches == maxCount)
+            {
+                part1Rows = checkRow;
+            }
+            else if (matches == maxCount - 1)
+            {
+                part2Rows = checkRow;
+            }
+        }
+
+        return (part1Rows, part2Rows);
+    }
+
+    (int, int) CheckGrid(IList<string> grid)
+    {
+        (int part1Lefts, int part2Lefts) = CheckColumns(grid);
+        (int part1Ups, int part2Ups) = CheckRows(grid);
+
+        return (part1Lefts + part1Ups * 100, part2Lefts + part2Ups * 100);
+    }
+
+    internal override string Part1()
+    {
+        return $"Columns and rows total: <+white>{part1}";
+    }
+
+    internal override string Part2()
+    {
+        return $"Smudged columns and rows total: <+white>{part2}";
+    }
+}