aoc2021/05/code.go

package main

import (
	"fmt"
	"io/ioutil"
	"log"
	"os"
	"strconv"
	"strings"
)

func readInput(file string) [][][]int {
	content, err := ioutil.ReadFile(file)
	if err != nil {
		log.Fatal(err)
	}

	lines := strings.Split(string(content), "\n")
	var points [][][]int
	for _, line := range lines {
		if line == "" {
			continue
		}

		pointsString := strings.Split(line, " -> ")
		if len(pointsString) != 2 {
			log.Fatal("Invalid line: ", line)
		}

		start := strings.Split(pointsString[0], ",")
		if len(start) != 2 {
			log.Fatal("Invalid start point: ", start)
		}

		startPoint := make([]int, 2)
		startPoint[0], err = strconv.Atoi(start[0])
		if err != nil {
			log.Fatal(err)
		}
		startPoint[1], err = strconv.Atoi(start[1])
		if err != nil {
			log.Fatal(err)
		}

		end := strings.Split(pointsString[1], ",")
		if len(end) != 2 {
			log.Fatal("Invalid end point: ", end)
		}
		endPoint := make([]int, 2)
		endPoint[0], err = strconv.Atoi(end[0])
		if err != nil {
			log.Fatal(err)
		}
		endPoint[1], err = strconv.Atoi(end[1])
		if err != nil {
			log.Fatal(err)
		}

		points = append(points, [][]int{startPoint, endPoint})
	}

	return points
}

func largest(points [][][]int, index int) int {
	largest := 0
	for _, point := range points {
		if point[0][index] > largest {
			largest = point[0][index]
		} else if point[1][index] > largest {
			largest = point[1][index]
		}
	}

	return largest
}

func makeDiagram(points [][][]int) [][]int {
	largestX := largest(points, 0)
	largestY := largest(points, 1)

	diagram := make([][]int, largestY-1)
	for i, _ := range diagram {
		diagram[i] = make([]int, largestX-1)
	}
	return diagram
}

func main() {
	if len(os.Args) < 2 {
		log.Fatal("Please provide a file name as argument")
	}

	input := readInput(os.Args[1])
	diagram := makeDiagram(input)
	fmt.Println(diagram)
}