day 4 part 1

AdventOfCode/Day04.cs

@@ -0,0 +1,111 @@
+namespace AdventOfCode;
+
+public class Day04 : BaseDay
+{
+    private readonly char[,] _input;
+    private readonly int _height;
+    private readonly int _width;
+
+    public Day04()
+    {
+        string[] lines = File.ReadAllLines(InputFilePath);
+
+        _input = new char[lines.Length, lines[0].Length];
+
+        for (int i = 0; i < lines.Length; i++)
+        {
+            for (int j = 0; j < lines[0].Length; j++)
+            {
+                _input[i, j] = lines[i][j];
+            }
+        }
+
+        _height = _input.GetLength(0);
+        _width = _input.GetLength(1);
+    }
+
+    public override ValueTask<string> Solve_1()
+    {
+        int result = 0;
+
+        for (int i = 0; i < _height; i++)
+        {
+            for (int j = 0; j < _width; j++)
+            {
+                result += CountXmases(i, j);
+            }
+        }
+
+        return new(result.ToString());
+    }
+
+    public override ValueTask<string> Solve_2()
+    {
+        return new("");
+    }
+
+    private int CountXmases(int i, int j)
+    {
+        int res = 0;
+
+        if (_input[i, j] != 'X')
+        {
+            return res;
+        }
+
+        // left to right
+        if (j <= _width - 4 && IsMas(_input[i, j + 1], _input[i, j + 2], _input[i, j + 3]))
+        {
+            res += 1;
+        }
+
+        // right to left
+        if (j >= 3 && IsMas(_input[i, j - 1], _input[i, j - 2], _input[i, j - 3]))
+        {
+            res += 1;
+        }
+
+        // top to bottom
+        if (i <= _height - 4 && IsMas(_input[i + 1, j], _input[i + 2, j], _input[i + 3, j]))
+        {
+            res += 1;
+        }
+
+        // bottom to top
+        if (i >= 3 && IsMas(_input[i - 1, j], _input[i - 2, j], _input[i - 3, j]))
+        {
+            res += 1;
+        }
+
+        // diagonal TL to BR
+        if (i <= _height - 4  && j <= _width - 4 && IsMas(_input[i + 1, j + 1], _input[i + 2, j + 2], _input[i + 3, j + 3]))
+        {
+            res += 1;
+        }
+
+        // diagonal TR to BL
+        if (i <= _height - 4 && j >= 3 && IsMas(_input[i + 1, j - 1], _input[i + 2, j - 2], _input[i + 3, j - 3]))
+        {
+            res += 1;
+        }
+
+        // diagonal BL to TR
+        if (i >= 3 && j <= _width - 4 && IsMas(_input[i - 1, j + 1], _input[i - 2, j + 2], _input[i - 3, j + 3]))
+        {
+            res += 1;
+        }
+
+        // diagonal BR to TL
+        if (i >= 3 && j >= 3 && IsMas(_input[i - 1, j - 1], _input[i - 2, j - 2], _input[i - 3, j - 3]))
+        {
+            res += 1;
+        }
+
+        return res;
+    }
+
+    private bool IsMas(char m, char a, char s)
+    {
+        return m == 'M' && a == 'A' && s == 'S';
+    }
+}