advent_of_code_2024/day_15/solution.go

package day_15

import (
	"fmt"
	"slices"
	"strings"
)

const (
	Wall     = '#'
	Player   = '@'
	Box      = 'O'
	Empty    = '.'
	WideBoxL = '['
	WideBoxR = ']'
)

const (
	InstUp    = '^'
	InstDown  = 'v'
	InstLeft  = '<'
	InstRight = '>'
)

type Warehouse [][]rune

func (w Warehouse) Print() {
	for _, line := range w {
		fmt.Println(string(line))
	}
}

func (w Warehouse) At(x, y int) rune {
	if x < 0 || y < 0 || x >= len(w[0]) || y >= len(w) {
		return Wall
	}
	return w[y][x]
}

// task:https://adventofcode.com/2024/day/13
func SolveBasic(input string) int {
	warehouse, instructions, rX, rY := load(input)

	for _, instr := range instructions {
		switch instr {
		case InstUp:
			rX, rY = moveUp(warehouse, rX, rY)
		case InstDown:
			rX, rY = moveDown(warehouse, rX, rY)
		case InstLeft:
			rX, rY = moveLeft(warehouse, rX, rY)
		case InstRight:
			rX, rY = moveRight(warehouse, rX, rY)
		default:
			panic("unknown instruction " + string(instr))
		}
	}
	sum := 0
	for y, line := range warehouse {
		for x, val := range line {
			if val == Box {
				sum += y*100 + x
			}
		}
	}
	return sum
}

// task:https://adventofcode.com/2024/day/12#part2
func SolveComplex(input string) int {
	warehouse, instructions, rX, rY := loadWide(input)

	for _, instr := range instructions {
		switch instr {
		case InstUp:
			rX, rY = moveWideUp(warehouse, rX, rY)
		case InstDown:
			rX, rY = moveWideDown(warehouse, rX, rY)
		case InstLeft:
			rX, rY = moveWideLeft(warehouse, rX, rY)
		case InstRight:
			rX, rY = moveWideRight(warehouse, rX, rY)
		default:
			panic("unknown instruction " + string(instr))
		}
	}
	sum := 0
	for y, line := range warehouse {
		for x, val := range line {
			if val == WideBoxL {
				sum += y*100 + x
			}
		}
	}
	return sum
}

func load(input string) (Warehouse, []rune, int, int) {
	substrings := strings.Split(input, "\n\n")
	warehouse := Warehouse{}
	rX := 0
	rY := 0
	for y, line := range strings.Split(substrings[0], "\n") {
		if strings.ContainsRune(line, Player) {
			rY = y
			rX = strings.IndexRune(line, Player)
		}
		warehouse = append(warehouse, []rune(line))
	}
	instructions := []rune(strings.ReplaceAll(substrings[1], "\n", ""))

	return warehouse, instructions, rX, rY
}

func loadWide(input string) (Warehouse, []rune, int, int) {
	substrings := strings.Split(input, "\n\n")
	warehouse := Warehouse{}
	rX := 0
	rY := 0
	for y, line := range strings.Split(substrings[0], "\n") {
		line = expandLine(line)
		if strings.ContainsRune(line, Player) {
			rY = y
			rX = strings.IndexRune(line, Player)
		}
		warehouse = append(warehouse, []rune(line))
	}
	instructions := []rune(strings.ReplaceAll(substrings[1], "\n", ""))

	return warehouse, instructions, rX, rY
}

func expandLine(line string) string {
	line = strings.ReplaceAll(line, "#", "##")
	line = strings.ReplaceAll(line, ".", "..")
	line = strings.ReplaceAll(line, "@", "@.")
	line = strings.ReplaceAll(line, "O", "[]")
	return line
}

func moveUp(warehouse Warehouse, x int, y int) (int, int) {
	if warehouse.At(x, y-1) == Wall {
		return x, y
	} else if warehouse.At(x, y-1) == Empty {
		warehouse[y][x] = Empty
		warehouse[y-1][x] = Player
		return x, y - 1
	} else {
		newY := y - 1
		for ; warehouse.At(x, newY) == Box; newY-- {
		}
		if warehouse.At(x, newY) == Empty {
			warehouse[newY][x] = Box
			warehouse[y-1][x] = Player
			warehouse[y][x] = Empty
			return x, y - 1
		}
	}
	return x, y
}

func moveDown(warehouse Warehouse, x int, y int) (int, int) {
	if warehouse.At(x, y+1) == Wall {
		return x, y
	} else if warehouse.At(x, y+1) == Empty {
		warehouse[y][x] = Empty
		warehouse[y+1][x] = Player
		return x, y + 1
	} else {
		newY := y + 1
		for ; warehouse.At(x, newY) == Box; newY++ {
		}
		if warehouse.At(x, newY) == Empty {
			warehouse[newY][x] = Box
			warehouse[y+1][x] = Player
			warehouse[y][x] = Empty
			return x, y + 1
		}
	}
	return x, y
}

func moveLeft(warehouse Warehouse, x int, y int) (int, int) {
	if warehouse.At(x-1, y) == Wall {
		return x, y
	} else if warehouse.At(x-1, y) == Empty {
		warehouse[y][x] = Empty
		warehouse[y][x-1] = Player
		return x - 1, y
	} else {
		newX := x - 1
		for ; warehouse.At(newX, y) == Box; newX-- {
		}
		if warehouse.At(newX, y) == Empty {
			warehouse[y][newX] = Box
			warehouse[y][x-1] = Player
			warehouse[y][x] = Empty
			return x - 1, y
		}
	}
	return x, y
}

func moveRight(warehouse Warehouse, x int, y int) (int, int) {
	if warehouse.At(x+1, y) == Wall {
		return x, y
	} else if warehouse.At(x+1, y) == Empty {
		warehouse[y][x] = Empty
		warehouse[y][x+1] = Player
		return x + 1, y
	} else {
		newX := x + 1
		for ; warehouse.At(newX, y) == Box; newX++ {
		}
		if warehouse.At(newX, y) == Empty {
			warehouse[y][newX] = Box
			warehouse[y][x+1] = Player
			warehouse[y][x] = Empty
			return x + 1, y
		}
	}
	return x, y
}

func moveWideUp(warehouse Warehouse, x int, y int) (int, int) {
	if warehouse.At(x, y-1) == Wall {
		return x, y
	} else if warehouse.At(x, y-1) == Empty {
		warehouse[y][x] = Empty
		warehouse[y-1][x] = Player
		return x, y - 1
	} else {
		type Point struct {
			x, y int
		}
		checkable := []Point{{x, y}}

		for i := 0; i < len(checkable); i++ {
			p := checkable[i]
			l := warehouse.At(p.x, p.y-1)
			if l == Wall {
				return x, y
			}
			if l == WideBoxL {
				if !slices.Contains(checkable, Point{p.x, p.y - 1}) {
					checkable = append(checkable, Point{p.x, p.y - 1})
				}
				if !slices.Contains(checkable, Point{p.x + 1, p.y - 1}) {
					checkable = append(checkable, Point{p.x + 1, p.y - 1})
				}
			}
			if l == WideBoxR {
				if !slices.Contains(checkable, Point{p.x, p.y - 1}) {
					checkable = append(checkable, Point{p.x, p.y - 1})
				}
				if !slices.Contains(checkable, Point{p.x - 1, p.y - 1}) {
					checkable = append(checkable, Point{p.x - 1, p.y - 1})
				}
			}
		}
		for i := len(checkable) - 1; i >= 0; i-- {
			p := checkable[i]
			warehouse[p.y-1][p.x] = warehouse[p.y][p.x]
			warehouse[p.y][p.x] = Empty
		}
		return x, y - 1
	}
}

func moveWideDown(warehouse Warehouse, x int, y int) (int, int) {
	if warehouse.At(x, y+1) == Wall {
		return x, y
	} else if warehouse.At(x, y+1) == Empty {
		warehouse[y][x] = Empty
		warehouse[y+1][x] = Player
		return x, y + 1
	} else {
		type Point struct {
			x, y int
		}
		checkable := []Point{{x, y}}

		for i := 0; i < len(checkable); i++ {
			p := checkable[i]
			l := warehouse.At(p.x, p.y+1)
			if l == Wall {
				return x, y
			}
			if l == WideBoxL {
				if !slices.Contains(checkable, Point{p.x, p.y + 1}) {
					checkable = append(checkable, Point{p.x, p.y + 1})
				}
				if !slices.Contains(checkable, Point{p.x + 1, p.y + 1}) {
					checkable = append(checkable, Point{p.x + 1, p.y + 1})
				}
			}
			if l == WideBoxR {
				if !slices.Contains(checkable, Point{p.x, p.y + 1}) {
					checkable = append(checkable, Point{p.x, p.y + 1})
				}
				if !slices.Contains(checkable, Point{p.x - 1, p.y + 1}) {
					checkable = append(checkable, Point{p.x - 1, p.y + 1})
				}
			}
		}
		for i := len(checkable) - 1; i >= 0; i-- {
			p := checkable[i]
			warehouse[p.y+1][p.x] = warehouse[p.y][p.x]
			warehouse[p.y][p.x] = Empty
		}
		return x, y + 1
	}
}

func moveWideLeft(warehouse Warehouse, x int, y int) (int, int) {
	if warehouse.At(x-1, y) == Wall {
		return x, y
	} else if warehouse.At(x-1, y) == Empty {
		warehouse[y][x] = Empty
		warehouse[y][x-1] = Player
		return x - 1, y
	} else {
		newX := x - 1
		for ; warehouse.At(newX, y) == WideBoxL || warehouse.At(newX, y) == WideBoxR; newX-- {
		}
		if warehouse.At(newX, y) == Empty {
			for tx := newX; tx < x-1; tx++ {
				warehouse[y][tx] = warehouse[y][tx+1]
			}
			warehouse[y][x-1] = Player
			warehouse[y][x] = Empty
			return x - 1, y
		}
	}
	return x, y
}

func moveWideRight(warehouse Warehouse, x int, y int) (int, int) {
	if warehouse.At(x+1, y) == Wall {
		return x, y
	} else if warehouse.At(x+1, y) == Empty {
		warehouse[y][x] = Empty
		warehouse[y][x+1] = Player
		return x + 1, y
	} else {
		newX := x + 1
		for ; warehouse.At(newX, y) == WideBoxL || warehouse.At(newX, y) == WideBoxR; newX++ {
		}
		if warehouse.At(newX, y) == Empty {
			for tx := newX; tx > x+1; tx-- {
				warehouse[y][tx] = warehouse[y][tx-1]
			}
			warehouse[y][x+1] = Player
			warehouse[y][x] = Empty
			return x + 1, y
		}
	}
	return x, y
}