AOC-2024/18/main.go

package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
	"strings"
	"time"
)

const FILE_PATH = "./input.txt"
const SIZE = 71
const BYTES = 1024

//const FILE_PATH = "./sample.txt"
//const SIZE = 7
//const BYTES = 12

func LoadInput(filename string) ([]string, error) {
	file, err := os.Open(filename)
	if err != nil {
		return nil, err
	}
	defer file.Close()

	var lines []string
	scanner := bufio.NewScanner(file)
	for scanner.Scan() {
		lines = append(lines, scanner.Text())
	}

	if err := scanner.Err(); err != nil {
		return nil, err
	}

	return lines, nil
}

type Vector2 struct {
	x int
	y int
}

type structuredInput = []Vector2

func TransformInput(lines []string) structuredInput {
	var result = make([]Vector2, len(lines))
	var numbs []string
	var x int
	var y int

	for i, line := range lines {
		numbs = strings.Split(line, ",")
		x, _ = strconv.Atoi(numbs[0])
		y, _ = strconv.Atoi(numbs[1])
		result[i] = Vector2{x, y}
	}

	return result
}

const (
	EMPTY = iota
	WALL  = iota
)

func generateGrid(size int, bytes int, memory []Vector2) [][]int {
	var result = make([][]int, size)

	for i := 0; i < size; i++ {
		result[i] = make([]int, size)
		for j := 0; j < size; j++ {
			result[i][j] = EMPTY
		}
	}

	for i := 0; i < bytes; i++ {
		result[memory[i].y][memory[i].x] = WALL
	}

	return result
}

func printField(field [][]int) {
	for y := 0; y < len(field); y++ {
		for x := 0; x < len(field[y]); x++ {
			if field[y][x] == EMPTY {
				fmt.Print(".")
			} else {
				fmt.Print("#")
			}
		}
		fmt.Println()
	}
}

var MOVEMENT = []Vector2{
	{1, 0},
	{0, 1},
	{-1, 0},
	{0, -1},
}

func add(a Vector2, b Vector2) Vector2 {
	return Vector2{a.x + b.x, a.y + b.y}
}

func isInBounds(position Vector2, bounds Vector2) bool {
	return position.x >= 0 && position.x < bounds.x && position.y >= 0 && position.y < bounds.y
}

func Part1(input structuredInput) int {
	var result = 0

	var start = Vector2{0, 0}
	var end = Vector2{SIZE - 1, SIZE - 1}
	var field = generateGrid(SIZE, BYTES, input)
	var bounds = Vector2{SIZE, SIZE}
	var score = make([][]int, SIZE)
	var poss = []Vector2{start}
	var point Vector2
	var index int
	var temp Vector2

	for i := 0; i < SIZE; i++ {
		score[i] = make([]int, SIZE)
		for j := 0; j < SIZE; j++ {
			score[i][j] = -1
		}
	}
	score[start.y][start.x] = 0

	for len(poss) > 0 {
		point = poss[0]
		index = 0
		for i := 1; i < len(poss); i++ {
			if score[point.y][point.x] > score[poss[i].y][poss[i].x] {
				point = poss[i]
				index = i
			}
		}

		if point == end {
			result = score[end.y][end.x]
			break
		}

		poss = append(poss[:index], poss[index+1:]...)
		for i := 0; i < len(MOVEMENT); i++ {
			temp = add(point, MOVEMENT[i])
			if isInBounds(temp, bounds) && score[temp.y][temp.x] == -1 && field[temp.y][temp.x] != WALL {
				score[temp.y][temp.x] = score[point.y][point.x] + 1
				poss = append(poss, temp)
			}
		}
	}

	return result
}

func canFinish(field [][]int, start Vector2, finish Vector2, bounds Vector2) bool {
	var visited = make([][]bool, len(field))

	for i := 0; i < len(visited); i++ {
		visited[i] = make([]bool, len(field[i]))
	}
	var poss = []Vector2{start}
	var point Vector2
	var temp Vector2

	for len(poss) > 0 {
		point = poss[0]
		poss = poss[1:]
		for i := 0; i < 4; i++ {
			temp = add(point, MOVEMENT[i])
			if isInBounds(temp, bounds) && !visited[temp.y][temp.x] && field[temp.y][temp.x] != WALL {
				poss = append(poss, temp)
				visited[temp.y][temp.x] = true
				if temp == finish {
					return true
				}
			}
		}
	}
	return false
}

func Part2(input structuredInput) int {
	var result = 0

	var start = Vector2{0, 0}
	var end = Vector2{SIZE - 1, SIZE - 1}
	var field = generateGrid(SIZE, BYTES, input)
	var bounds = Vector2{SIZE, SIZE}
	i := BYTES

	for canFinish(field, start, end, bounds) {
		field[input[i].y][input[i].x] = WALL
		i++
	}
	i -= 1

	fmt.Printf("%d,%d\n", input[i].x, input[i].y)

	return result
}

func main() {
	var start time.Time
	var elapsed time.Duration = 0
	input, err := LoadInput(FILE_PATH)
	if err != nil {
		fmt.Println("Error loading input:", err)
		return
	}

	structuredInput := TransformInput(input)
	fmt.Println("Structured Input:", structuredInput)

	start = time.Now()
	fmt.Println("Solution Part 1: ", Part1(structuredInput))
	elapsed = time.Since(start)
	fmt.Printf("Part 1 took %s\n", elapsed)

	start = time.Now()
	fmt.Println("Solution Part 2: ", Part2(structuredInput))
	elapsed = time.Since(start)
	fmt.Printf("Part 2 took %s\n", elapsed)
}