feat(2025-04): Add day 4

2026-07-13 03:03:46 +00:00 · 2025-12-04 12:49:03 +00:00
parent 4eaa778adb
commit af8d99e953
8 changed files with 594 additions and 2 deletions
@@ -0,0 +1,131 @@
+using System.Text;
+
+namespace AOC.Helpers;
+
+public static class TwoDimensionalArrays
+{
+    public static char[,] Make2DArrayFromStringArray(string[] stringArray)
+    {
+        int rows = stringArray.Length;
+        int cols = stringArray[0].Length;
+
+        char[,] array = new char[rows, cols];
+
+        for (int r = 0; r < rows; r++)
+        {
+            for (int c = 0; c < cols; c++)
+            {
+                array[r, c] = stringArray[r][c];
+            }
+        }
+
+        return array;
+    }
+
+    public static string TwoDimensionalArrayToString(char[,] array)
+    {
+        int rows = array.GetLength(0);
+        int cols = array.GetLength(1);
+
+        StringBuilder sb = new(rows * (cols + 1)); // performance optimisation
+
+        for (int r = 0; r < rows; r++)
+        {
+            for (int c = 0; c < cols; c++)
+            {
+                sb.Append(array[r, c]);
+            }
+
+            sb.AppendLine(); // end of row
+        }
+
+        return sb.ToString();
+    }
+
+    /// <summary>
+    ///     Enumerates all cells in a 2D array, returning each cell's row index,
+    ///     column index, and value.
+    /// </summary>
+    /// <typeparam name="T">The element type of the 2D array.</typeparam>
+    /// <param name="grid">The 2D array to enumerate.</param>
+    /// <returns>
+    ///     An <see cref="IEnumerable{T}" /> of tuples containing the row index,
+    ///     column index, and value of each cell in the array, iterated in row-major order.
+    /// </returns>
+    /// <example>
+    ///     The following example prints every cell in a character grid:
+    ///     <code>
+    /// char[,] grid = {
+    ///     { 'A', 'B', 'C' },
+    ///     { 'D', 'E', 'F' }
+    /// };
+    /// 
+    /// foreach (var (row, column, value) in Cells(grid))
+    /// {
+    ///     Console.WriteLine($"[{row}, {column}] = {value}");
+    /// }
+    /// </code>
+    ///     This produces:
+    ///     <code>
+    /// [0, 0] = A
+    /// [0, 1] = B
+    /// [0, 2] = C
+    /// [1, 0] = D
+    /// [1, 1] = E
+    /// [1, 2] = F
+    /// </code>
+    /// </example>
+    public static IEnumerable<(int row, int column, T value)> Cells<T>(T[,] grid)
+    {
+        int rows = grid.GetLength(0);
+        int cols = grid.GetLength(1);
+
+        for (int r = 0; r < rows; r++)
+        {
+            for (int c = 0; c < cols; c++)
+            {
+                yield return (r, c, grid[r, c]);
+            }
+        }
+    }
+
+    public static List<(int row, int column)> CheckAllSurroundingCellsForCharacter(
+        char[,] array,
+        int startRow,
+        int startColumn,
+        char characterToCheckFor)
+    {
+        int totalRows = array.GetLength(0);
+        int totalColumns = array.GetLength(1);
+
+        List<(int row, int column)> results = new();
+
+        for (int rowOffset = -1; rowOffset <= 1; rowOffset++)
+        {
+            for (int colOffset = -1; colOffset <= 1; colOffset++)
+            {
+                // Skip the centre cell
+                if (rowOffset == 0 && colOffset == 0)
+                {
+                    continue;
+                }
+
+                int row = startRow + rowOffset;
+                int column = startColumn + colOffset;
+
+                // Bounds check
+                if (row < 0 || row >= totalRows || column < 0 || column >= totalColumns)
+                {
+                    continue;
+                }
+
+                if (array[row, column] == characterToCheckFor)
+                {
+                    results.Add((row, column));
+                }
+            }
+        }
+
+        return results;
+    }
+}