feat(2024): refactor day 4

Refactored Day 4 of 2024 to use the common framework. Successfully migrated solution and integrated it into the runner.

Author: markkovari

2024/golang/cmd/day04.go

@@ -0,0 +1,84 @@
+package main
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/markkovari/advent_of_code/aoc-go-common"
+)
+
+type Day04 struct{}
+
+func (d Day04) Part1(input string) string {
+	grid := parse(input)
+	count := 0
+	word := "XMAS"
+	rows := len(grid)
+	cols := len(grid[0])
+
+	dirs := [][2]int{
+		{0, 1}, {0, -1}, {1, 0}, {-1, 0},
+		{1, 1}, {1, -1}, {-1, 1}, {-1, -1},
+	}
+
+	for r := 0; r < rows; r++ {
+		for c := 0; c < cols; c++ {
+			for _, dir := range dirs {
+				if check(grid, r, c, dir, word) {
+					count++
+				}
+			}
+		}
+	}
+	return fmt.Sprintf("%d", count)
+}
+
+func (d Day04) Part2(input string) string {
+	grid := parse(input)
+	count := 0
+	rows := len(grid)
+	cols := len(grid[0])
+
+	for r := 1; r < rows-1; r++ {
+		for c := 1; c < cols-1; c++ {
+			if grid[r][c] == 'A' {
+				// M.M
+				// .A.
+				// S.S
+				tl := grid[r-1][c-1]
+				tr := grid[r-1][c+1]
+				bl := grid[r+1][c-1]
+				br := grid[r+1][c+1]
+
+				if ((tl == 'M' && br == 'S') || (tl == 'S' && br == 'M')) &&
+				   ((tr == 'M' && bl == 'S') || (tr == 'S' && bl == 'M')) {
+					count++
+				}
+			}
+		}
+	}
+	return fmt.Sprintf("%d", count)
+}
+
+func parse(input string) [][]rune {
+	var grid [][]rune
+	for _, line := range strings.Split(input, "\n") {
+		if line == "" { continue }
+		grid = append(grid, []rune(line))
+	}
+	return grid
+}
+
+func check(grid [][]rune, r, c int, dir [2]int, word string) bool {
+	for i := 0; i < len(word); i++ {
+		nr, nc := r+dir[0]*i, c+dir[1]*i
+		if nr < 0 || nr >= len(grid) || nc < 0 || nc >= len(grid[0]) || grid[nr][nc] != rune(word[i]) {
+			return false
+		}
+	}
+	return true
+}
+
+func main() {
+	common.Run(2024, 4, Day04{})
+}