advent_of_code_2024/day_15/solution.go

package day_15

import (
	"strings"
)

const (
	Wall   = '#'
	Player = '@'
	Box    = 'O'
	Empty  = '.'
)
const (
	InstUp    = '^'
	InstDown  = 'v'
	InstLeft  = '<'
	InstRight = '>'
)

type Warehouse [][]rune

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 {
	return 0
}

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 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
}