2024 day 1 part 1 - initial version

2024/day-04/go.mod

@@ -0,0 +1,3 @@
+module mziesel.nl/aoc/d4
+
+go 1.23.0

2024/day-04/input_test.txt

@@ -0,0 +1,10 @@
+MMMSXXMASM
+MSAMXMSMSA
+AMXSXMAAMM
+MSAMASMSMX
+XMASAMXAMM
+XXAMMXXAMA
+SMSMSASXSS
+SAXAMASAAA
+MAMMMXMMMM
+MXMXAXMASX

2024/day-04/main.go

@@ -0,0 +1,108 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+)
+
+func main() {
+	content, err := os.ReadFile("./input_test.txt")
+	if err != nil {
+		log.Fatalf("failed to open file: %s\n", err)
+	}
+
+	var field [][]string
+
+	x_axis := 0
+	y_axis := 0
+
+	for _, b := range content {
+		char := string(b)
+		if char == "\n" {
+			x_axis++
+			y_axis = 0
+			continue
+		}
+
+		if y_axis == 0 {
+			field = append(field, make([]string, 0))
+		}
+
+		field[x_axis] = append(field[x_axis], char)
+
+		y_axis++
+	}
+
+	var found [][]pos
+
+	for x, _ := range field {
+		for y, _ := range field[x] {
+			// empty array for the found chars
+			seq := []pos{}
+			checkXMAS(field, x, y, seq, &found)
+		}
+	}
+
+	fmt.Println("found: ", len(found))
+}
+
+type pos struct {
+	X int
+	Y int
+}
+
+func seqToString(field [][]string, seq []pos) string {
+	str := ""
+	for _, p := range seq {
+		str += field[p.X][p.Y]
+	}
+	return str
+}
+
+func checkXMAS(field [][]string, x int, y int, current_seq []pos, found *[][]pos) {
+	bound_x := len(field)
+	if x == -1 || x >= bound_x {
+		return
+	}
+	bound_y := len(field[x])
+	if y == -1 || y >= bound_y {
+		return
+	}
+
+	char := field[x][y]
+
+	seq_str := seqToString(field, current_seq)
+	// fmt.Printf("x: %d y: %d seq: '%s' curr_char: '%s'\n", x, y, seq_str, char)
+
+	if (seq_str == "" && char == "X") ||
+		(seq_str == "X" && char == "M") ||
+		(seq_str == "XM" && char == "A") ||
+		(seq_str == "XMA" && char == "S") {
+
+		pos := pos{X: x, Y: y}
+		current_seq = append(current_seq, pos)
+	} else {
+		return
+	}
+
+	if seqToString(field, current_seq) == "XMAS" {
+		*found = append(*found, current_seq)
+	}
+
+	//   y
+	// x 0 1 2 3
+	//   0 1 2 3
+	//   0 1 2 3
+	//   0 1 2 3
+
+	checkXMAS(field, x+1, y, current_seq, found)
+	checkXMAS(field, x-1, y, current_seq, found)
+	checkXMAS(field, x, y+1, current_seq, found)
+	checkXMAS(field, x, y-1, current_seq, found)
+
+	checkXMAS(field, x+1, y+1, current_seq, found)
+	checkXMAS(field, x+1, y-1, current_seq, found)
+	checkXMAS(field, x-1, y+1, current_seq, found)
+	checkXMAS(field, x-1, y-1, current_seq, found)
+}