day 06 partial solution

solutions/alessio/day05/go.mod

@@ -1,3 +1,3 @@
-module aoc4
+module aoc5
 
 go 1.23.3

solutions/alessio/day06/day06.go

@@ -0,0 +1,136 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"strings"
+)
+
+func check(e error) {
+	if e != nil {
+		panic(e)
+	}
+}
+
+type Cell struct {
+	r, c int
+}
+
+func part1(lines []string) {
+	// see https://go.dev/blog/maps#key-types for more details about this implementation vs using a map of maps
+	rows := len(lines)
+	cols := len(lines[0])
+	var startRow, startCol int
+	found := false
+	for r := range rows {
+		for c := range cols {
+			if lines[r][c] == '^' {
+				startRow = r
+				startCol = c
+				found = true
+				break
+			}
+		}
+		if found {
+			break
+		}
+	}
+
+	r, c := startRow, startCol
+	dirR, dirC := -1, 0 // up
+	visited := make(map[Cell]bool)
+	for {
+		if lines[r][c] != '#' && !visited[Cell{r, c}] {
+			visited[Cell{r, c}] = true
+		}
+		nextR, nextC := r+dirR, c+dirC
+		if nextR < 0 || nextC < 0 || nextR >= rows || nextC >= cols {
+			break
+		}
+		if lines[nextR][nextC] == '#' {
+			dirR, dirC = dirC, -dirR
+		}
+		r += dirR
+		c += dirC
+	}
+
+	fmt.Println(len(visited))
+}
+
+type VisitedCellKey struct {
+	r, c, rDir, cDir int
+}
+
+func part2(lines []string) {
+	rows := len(lines)
+	cols := len(lines[0])
+	var startRow, startCol int
+	found := false
+	for r := range rows {
+		for c := range cols {
+			if lines[r][c] == '^' {
+				startRow = r
+				startCol = c
+				found = true
+				break
+			}
+		}
+		if found {
+			break
+		}
+	}
+
+	loops := make(map[Cell]bool)
+	for r := range rows {
+		for c := range cols {
+			if lines[r][c] == '.' {
+				visited := make(map[VisitedCellKey]bool)
+				// temporary put a block here
+				lines[r] = lines[r][:c] + "#" + lines[r][c+1:]
+
+				i, j := startRow, startCol
+				dirR, dirC := -1, 0 // up
+				for {
+					isVisited := visited[VisitedCellKey{i, j, dirR, dirC}]
+					if lines[i][j] != '#' && !isVisited {
+						visited[VisitedCellKey{i, j, dirR, dirC}] = true
+					}
+					if lines[i][j] != '#' && isVisited {
+						// fmt.Printf("Found loop with block in (%d, %d)\n", r, c)
+						loops[Cell{r, c}] = true
+						break
+					}
+					nextR, nextC := i+dirR, j+dirC
+					if nextR < 0 || nextC < 0 || nextR >= rows || nextC >= cols {
+						break
+					}
+					if lines[nextR][nextC] == '#' {
+						dirR, dirC = dirC, -dirR
+						isVisited = visited[VisitedCellKey{i, j, dirR, dirC}]
+						if isVisited {
+							loops[Cell{r, c}] = true
+							break
+						} else {
+							visited[VisitedCellKey{i, j, dirR, dirC}] = true
+						}
+					}
+					i += dirR
+					j += dirC
+				}
+				// backtrack
+				lines[r] = lines[r][:c] + "." + lines[r][c+1:]
+			}
+		}
+	}
+	fmt.Println(len(loops))
+}
+
+func main() {
+	data, err := os.ReadFile("./input06.txt")
+	check(err)
+
+	lines := strings.Split(strings.Trim(string(data), "\r\n"), "\r\n")
+
+	// part1(lines)
+	part2(lines)
+}

solutions/alessio/day06/go.mod

@@ -0,0 +1,3 @@
+module aoc6
+
+go 1.23.3

solutions/alessio/day06/input06.txt

@@ -0,0 +1,130 @@
+................#.................#.#...........................#.#..................#............................................
+..........#................#...........#...................#.#....................................................................
+....#......#......#............#.#........#..........#.......#.......#...#........#..........#.........................#..........
+..................#............#.....##...............#..#.....................#...........#......................................
+#.........#.............................................................#........#............#........#.....#...#...........#....
+.....#...#......#..................................................#........#..................#......#.......................#...
+#.................................................#......................#......#...................................#.............
+...#.#...#.....................................#.......................#.........#..................................#....#........
+..............................................#..............#...#...........##..........................#.......#............#...
+........#.#.......#.................##.......................#..........#...........................#...#.........................
+.................#..............................#.................#............#....#.....#.......................................
+.................................................................#......#............#.#.#..................#.....................
+.#..........#......#...#.......#..........................#....................#.#.............................#..................
+...............#.....##.......#..#...###......#......................#.................................#.#......#..#..............
+#.....................#......................................#..........#...............#........#...............#...#.#..........
+.......................................#..................#.........................#.............................................
+.......................#...............................................................#........................#...........#.....
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