aoc2023/11/code.go

package main

import (
	"bufio"
	"fmt"
	"log"
	"os"
	"strings"
)

type Point struct {
	y, x      int
	direction int
}

type Universe struct {
	galaxies        []Point
	occupiedRows    map[int]bool
	occupiedColumns map[int]bool
}

func readInput(file *os.File) Universe {
	scanner := bufio.NewScanner(file)
	var universe Universe
	universe.occupiedRows = make(map[int]bool)
	universe.occupiedColumns = make(map[int]bool)

	index := 0
	for scanner.Scan() {
		line := scanner.Text()
		if line == "" {
			break
		}

		if strings.Contains(line, "#") {
			universe.occupiedRows[index] = true
			for i := range line {
				if line[i] == '#' {
					universe.galaxies = append(universe.galaxies, Point{y: index, x: i})
					universe.occupiedColumns[i] = true
				}
			}
		}

		index++
	}

	return universe
}

func distances(universe Universe, multiple int) int {
	var result int
	edge := len(universe.galaxies)
	for i := range universe.galaxies {
		for j := i + 1; j < edge; j++ {
			distance := 0
			for y := universe.galaxies[i].y + 1; y <= universe.galaxies[j].y; y++ {
				if universe.occupiedRows[y] {
					distance++
				} else {
					distance += multiple
				}
			}

			start := universe.galaxies[i].x + 1
			end := universe.galaxies[j].x
			if start > end {
				start, end = end, start
				start++
				end--
			}

			for ; start <= end; start++ {
				if universe.occupiedColumns[start] {
					distance++
				} else {
					distance += multiple
				}
			}

			result += distance
		}
	}

	return result
}

func main() {
	if len(os.Args) < 2 {
		log.Fatal("You need to specify a file!")
	}

	filePath := os.Args[1]
	file, err := os.Open(filePath)
	if err != nil {
		log.Fatalf("Failed to open %s!\n", filePath)

	}

	universe := readInput(file)
	fmt.Println("Part1:", distances(universe, 2))
	fmt.Println("Part2:", distances(universe, 1000000))
}