Day 06. part 2

data.go

@@ -18,3 +18,6 @@ var Day04Data string
 
 //go:embed day_05/data.txt
 var Day05Data string
+
+//go:embed day_06/data.txt
+var Day06Data string

day_06/data.txt

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

day_06/example_data.txt

@@ -0,0 +1,10 @@
+....#.....
+.........#
+..........
+..#.......
+.......#..
+..........
+.#..^.....
+........#.
+#.........
+......#...

day_06/solution.go

@@ -0,0 +1,161 @@
+package day_06
+
+import (
+	"strings"
+)
+
+type Direction int
+
+const (
+	UP    Direction = iota
+	RIGHT Direction = iota
+	DOWN  Direction = iota
+	LEFT  Direction = iota
+)
+
+const (
+	VISITED  = 'X'
+	OCCUPIED = '#'
+	FREE     = '.'
+)
+
+var toDirections = map[rune]Direction{
+	'^': UP,
+	'>': RIGHT,
+	'v': DOWN,
+	'<': LEFT,
+}
+
+var fromDirections = map[Direction]rune{
+	UP:    '^',
+	RIGHT: '>',
+	DOWN:  'v',
+	LEFT:  '<',
+}
+
+// task:https://adventofcode.com/2024/day/5
+// short summary - count visited steps
+func SolveBasic(input string) int {
+	grid := visitationGrid(input)
+
+	sum := 0
+	for _, row := range grid {
+		for _, value := range row {
+			if value == VISITED {
+				sum++
+			}
+		}
+	}
+	return sum
+}
+
+// task:https://adventofcode.com/2024/day/5#part2
+// short summary - find all position that will create an infinite loop
+func SolveComplex(input string) int {
+	grid := visitationGrid(input)
+
+	dirGrid := loadGrid(input)
+	startX, startY, startDir := findPlayer(dirGrid)
+	dirGrid[startY][startX] = FREE
+
+	positions := 0
+
+	for y, row := range grid {
+		for x, value := range row {
+			if value == VISITED && dirGrid[y][x] == FREE {
+				dirGrid[y][x] = OCCUPIED
+
+				curX := startX
+				curY := startY
+				curDir := startDir
+
+				for inGrid(dirGrid, curX, curY) {
+					if dirGrid[curY][curX] == fromDirections[curDir] {
+						// we visited a same point second time in the same direction
+						// which means we are in an infinite list
+						positions++
+						break
+					}
+					dirGrid[curY][curX] = fromDirections[curDir]
+					curX, curY, curDir = nextSpot(dirGrid, curX, curY, curDir)
+
+				}
+				dirGrid[y][x] = FREE
+				clearDirGrid(dirGrid)
+			}
+		}
+	}
+	return positions
+}
+
+func clearDirGrid(grid [][]rune) {
+	for y, row := range grid {
+		for x, value := range row {
+			if value != OCCUPIED {
+				grid[y][x] = FREE
+			}
+		}
+	}
+}
+
+func nextSpot(grid [][]rune, x int, y int, dir Direction) (int, int, Direction) {
+	for {
+		nx, ny := calculateNext(x, y, dir)
+		if !inGrid(grid, nx, ny) {
+			return nx, ny, dir
+		} else if grid[ny][nx] != OCCUPIED {
+			return nx, ny, dir
+		} else {
+			dir = (dir + 1) % 4
+		}
+	}
+}
+
+func calculateNext(x int, y int, dir Direction) (int, int) {
+	switch dir {
+	case UP:
+		return x, y - 1
+	case RIGHT:
+		return x + 1, y
+	case DOWN:
+		return x, y + 1
+	case LEFT:
+		return x - 1, y
+	}
+	panic("unknown direction")
+}
+
+func inGrid(grid [][]rune, x int, y int) bool {
+	return x >= 0 && y >= 0 && x < len(grid[0]) && y < len(grid)
+}
+
+func findPlayer(grid [][]rune) (int, int, Direction) {
+	for y, row := range grid {
+		for x, value := range row {
+			if dir, present := toDirections[value]; present {
+				return x, y, dir
+			}
+		}
+	}
+	panic("Couldn't find player")
+}
+
+func loadGrid(input string) [][]rune {
+	substrings := strings.Split(input, "\n")
+	var grid [][]rune
+	for _, line := range substrings {
+		grid = append(grid, []rune(line))
+	}
+	return grid
+}
+
+func visitationGrid(input string) [][]rune {
+	grid := loadGrid(input)
+	x, y, dir := findPlayer(grid)
+
+	for inGrid(grid, x, y) {
+		grid[y][x] = VISITED
+		x, y, dir = nextSpot(grid, x, y, dir)
+	}
+	return grid
+}

day_06/solution_test.go

@@ -0,0 +1,24 @@
+package day_06_test
+
+import (
+	"advent_of_code_2024/day_06"
+	_ "embed"
+	"testing"
+)
+
+//go:embed example_data.txt
+var ExampleData string
+
+func TestBasicSolutionExample(t *testing.T) {
+	result := day_06.SolveBasic(ExampleData)
+	if result != 41 {
+		t.Fatalf("Expected 41 received %d", result)
+	}
+}
+
+func TestComplexSolutionExample(t *testing.T) {
+	result := day_06.SolveComplex(ExampleData)
+	if result != 6 {
+		t.Fatalf("Expected 6 received %d", result)
+	}
+}

main.go

@@ -6,6 +6,7 @@ import (
 	"advent_of_code_2024/day_03"
 	"advent_of_code_2024/day_04"
 	"advent_of_code_2024/day_05"
+	"advent_of_code_2024/day_06"
 	_ "embed"
 	"fmt"
 	"os"
@@ -35,6 +36,10 @@ func main() {
 		fmt.Printf("Day 05. Basic: %d\n", day_05.SolveBasic(Day05Data)) // 2560
 	case "05-complex":
 		fmt.Printf("Day 05. Complex: %d\n", day_05.SolveComplex(Day05Data)) // 63013756
+	case "06-basic":
+		fmt.Printf("Day 06. Basic: %d\n", day_06.SolveBasic(Day06Data)) //
+	case "06-complex":
+		fmt.Printf("Day 06. Complex: %d\n", day_06.SolveComplex(Day06Data)) //
 	}
 }