aoc 6 in go

day6.go

package aoc

import (
	"fmt"
	"regexp"
	"strconv"
)

func newChristmasLightsPart2() [1000][1000]int {
	// 1 million lights in a 1000x1000 grid
	return [1000][1000]int{}
}

func newChristmasLights() [1000][1000]bool {
	// 1 million lights in a 1000x1000 grid
	return [1000][1000]bool{}
}

func ChangeChristmasLights(lights *[1000][1000]bool, s string) {

	regex := "(turn on|turn off|toggle) ([0-9]+),([0-9]+) through ([0-9]+),([0-9]+)"

	r, err := regexp.Compile(regex)
	if err != nil {
		fmt.Println("Error", err)
	}

	matches := r.FindStringSubmatch(s)

	action := matches[1]

	x1, _ := strconv.Atoi(matches[2])
	y1, _ := strconv.Atoi(matches[3])
	x2, _ := strconv.Atoi(matches[4])
	y2, _ := strconv.Atoi(matches[5])

	for x := x1; x <= x2; x++ {
		for y := y1; y <= y2; y++ {

			if action == "turn on" {
				lights[x][y] = true
			} else if action == "turn off" {
				lights[x][y] = false
			} else if action == "toggle" {
				lights[x][y] = !lights[x][y]
			}

		}
	}
}

func christmasLightsOn(lights *[1000][1000]bool) int {

	cnt := 0
	for x := 0; x < 1000; x++ {
		for y := 0; y < 1000; y++ {

			if lights[x][y] {
				cnt++
			}

		}
	}

	return cnt
}

func christmasLightsBrightness(lights *[1000][1000]int) int {

	cnt := 0
	for x := 0; x < 1000; x++ {
		for y := 0; y < 1000; y++ {
			cnt += lights[x][y]
		}
	}

	return cnt
}

func ChangeChristmasLightsPart2(lights *[1000][1000]int, s string) {

	regex := "(turn on|turn off|toggle) ([0-9]+),([0-9]+) through ([0-9]+),([0-9]+)"

	r, err := regexp.Compile(regex)
	if err != nil {
		fmt.Println("Error", err)
	}

	matches := r.FindStringSubmatch(s)

	action := matches[1]

	x1, _ := strconv.Atoi(matches[2])
	y1, _ := strconv.Atoi(matches[3])
	x2, _ := strconv.Atoi(matches[4])
	y2, _ := strconv.Atoi(matches[5])

	for x := x1; x <= x2; x++ {
		for y := y1; y <= y2; y++ {

			if action == "turn on" {
				lights[x][y]++
			} else if action == "turn off" {
				if lights[x][y] > 0 {
					lights[x][y]--
				}
			} else if action == "toggle" {
				lights[x][y] = lights[x][y] + 2
			}

		}
	}
}

day6_test.go

package aoc

import (
	"io/ioutil"
	"strings"
	"testing"

	"github.com/stretchr/testify/assert"
)

func TestChristmasLights(t *testing.T) {

	lights1 := newChristmasLights()

	ChangeChristmasLights(&lights1, "turn on 0,0 through 999,999")
	// turn on (or leave on) every light
	assert.Equal(t, 1000000, christmasLightsOn(&lights1))

	lights2 := newChristmasLights()
	ChangeChristmasLights(&lights2, "toggle 0,0 through 999,0")
	// toggle the first line of 1000 lights, turning off the ones that were on, and turning on the ones that were off
	assert.Equal(t, 1000, christmasLightsOn(&lights2))

	ChangeChristmasLights(&lights1, "turn off 499,499 through 500,500")
	// turn off (or leave off) the middle four lights
	assert.Equal(t, 1000000-4, christmasLightsOn(&lights1))
}

func TestDay6Questions(t *testing.T) {
	data, err := ioutil.ReadFile("../day6_input")
	if err != nil {
		t.Fatal("Error ", err)
	}
	s := string(data)

	arr := strings.Split(s, "\n")

	lights1 := newChristmasLights()
	lights2 := newChristmasLightsPart2()
	for _, val := range arr {
		if len(val) > 0 {
			ChangeChristmasLights(&lights1, val)
			ChangeChristmasLightsPart2(&lights2, val)
		}
	}

	// part 1 and 2
	assert.Equal(t, 400410, christmasLightsOn(&lights1))
	assert.Equal(t, 15343601, christmasLightsBrightness(&lights2))
}