AdventOfCode2020/17/main.go

package main

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

func main() {
	start := time.Now()
	partOne()
	duration := time.Since(start)
	partTwo()
	duration2 := time.Since(start)
	fmt.Printf("p1: %s, p2: %s\n", duration, duration2-duration)
}

type cell struct {
	x int // length
	y int // width
	z int // depth
	w int // spissitude
}

type universe struct {
	cells map[cell]bool
	hyper bool // true: 4-dimensional; false: 3-dimensional
}

func makeNeighborsList(c cell, hyper bool) []cell {
	cells := []cell{}
	if hyper {
		cells = append(cells, []cell{
			// outward...?
			// above
			{x: c.x + 1, y: c.y + 1, z: c.z + 1, w: c.w + 1},
			{x: c.x + 1, y: c.y, z: c.z + 1, w: c.w + 1},
			{x: c.x + 1, y: c.y - 1, z: c.z + 1, w: c.w + 1},
			{x: c.x, y: c.y + 1, z: c.z + 1, w: c.w + 1},
			{x: c.x, y: c.y, z: c.z + 1, w: c.w + 1},
			{x: c.x, y: c.y - 1, z: c.z + 1, w: c.w + 1},
			{x: c.x - 1, y: c.y + 1, z: c.z + 1, w: c.w + 1},
			{x: c.x - 1, y: c.y, z: c.z + 1, w: c.w + 1},
			{x: c.x - 1, y: c.y - 1, z: c.z + 1, w: c.w + 1},

			// same layer
			{x: c.x + 1, y: c.y + 1, z: c.z, w: c.w + 1},
			{x: c.x + 1, y: c.y, z: c.z, w: c.w + 1},
			{x: c.x + 1, y: c.y - 1, z: c.z, w: c.w + 1},
			{x: c.x, y: c.y + 1, z: c.z, w: c.w + 1},
			{x: c.x, y: c.y, z: c.z, w: c.w + 1},
			{x: c.x, y: c.y - 1, z: c.z, w: c.w + 1},
			{x: c.x - 1, y: c.y + 1, z: c.z, w: c.w + 1},
			{x: c.x - 1, y: c.y, z: c.z, w: c.w + 1},
			{x: c.x - 1, y: c.y - 1, z: c.z, w: c.w + 1},

			// below
			{x: c.x + 1, y: c.y + 1, z: c.z - 1, w: c.w + 1},
			{x: c.x + 1, y: c.y, z: c.z - 1, w: c.w + 1},
			{x: c.x + 1, y: c.y - 1, z: c.z - 1, w: c.w + 1},
			{x: c.x, y: c.y + 1, z: c.z - 1, w: c.w + 1},
			{x: c.x, y: c.y, z: c.z - 1, w: c.w + 1},
			{x: c.x, y: c.y - 1, z: c.z - 1, w: c.w + 1},
			{x: c.x - 1, y: c.y + 1, z: c.z - 1, w: c.w + 1},
			{x: c.x - 1, y: c.y, z: c.z - 1, w: c.w + 1},
			{x: c.x - 1, y: c.y - 1, z: c.z - 1, w: c.w + 1},
			// inward...?
			// above
			{x: c.x + 1, y: c.y + 1, z: c.z + 1, w: c.w - 1},
			{x: c.x + 1, y: c.y, z: c.z + 1, w: c.w - 1},
			{x: c.x + 1, y: c.y - 1, z: c.z + 1, w: c.w - 1},
			{x: c.x, y: c.y + 1, z: c.z + 1, w: c.w - 1},
			{x: c.x, y: c.y, z: c.z + 1, w: c.w - 1},
			{x: c.x, y: c.y - 1, z: c.z + 1, w: c.w - 1},
			{x: c.x - 1, y: c.y + 1, z: c.z + 1, w: c.w - 1},
			{x: c.x - 1, y: c.y, z: c.z + 1, w: c.w - 1},
			{x: c.x - 1, y: c.y - 1, z: c.z + 1, w: c.w - 1},

			// same layer
			{x: c.x + 1, y: c.y + 1, z: c.z, w: c.w - 1},
			{x: c.x + 1, y: c.y, z: c.z, w: c.w - 1},
			{x: c.x + 1, y: c.y - 1, z: c.z, w: c.w - 1},
			{x: c.x, y: c.y + 1, z: c.z, w: c.w - 1},
			{x: c.x, y: c.y, z: c.z, w: c.w - 1},
			{x: c.x, y: c.y - 1, z: c.z, w: c.w - 1},
			{x: c.x - 1, y: c.y + 1, z: c.z, w: c.w - 1},
			{x: c.x - 1, y: c.y, z: c.z, w: c.w - 1},
			{x: c.x - 1, y: c.y - 1, z: c.z, w: c.w - 1},

			// below
			{x: c.x + 1, y: c.y + 1, z: c.z - 1, w: c.w - 1},
			{x: c.x + 1, y: c.y, z: c.z - 1, w: c.w - 1},
			{x: c.x + 1, y: c.y - 1, z: c.z - 1, w: c.w - 1},
			{x: c.x, y: c.y + 1, z: c.z - 1, w: c.w - 1},
			{x: c.x, y: c.y, z: c.z - 1, w: c.w - 1},
			{x: c.x, y: c.y - 1, z: c.z - 1, w: c.w - 1},
			{x: c.x - 1, y: c.y + 1, z: c.z - 1, w: c.w - 1},
			{x: c.x - 1, y: c.y, z: c.z - 1, w: c.w - 1},
			{x: c.x - 1, y: c.y - 1, z: c.z - 1, w: c.w - 1},
		}...)
	}

	// "normal" space
	cells = append(cells, []cell{
		// above
		{x: c.x + 1, y: c.y + 1, z: c.z + 1, w: c.w},
		{x: c.x + 1, y: c.y, z: c.z + 1, w: c.w},
		{x: c.x + 1, y: c.y - 1, z: c.z + 1, w: c.w},
		{x: c.x, y: c.y + 1, z: c.z + 1, w: c.w},
		{x: c.x, y: c.y, z: c.z + 1, w: c.w},
		{x: c.x, y: c.y - 1, z: c.z + 1, w: c.w},
		{x: c.x - 1, y: c.y + 1, z: c.z + 1, w: c.w},
		{x: c.x - 1, y: c.y, z: c.z + 1, w: c.w},
		{x: c.x - 1, y: c.y - 1, z: c.z + 1, w: c.w},

		// same layer
		{x: c.x + 1, y: c.y + 1, z: c.z, w: c.w},
		{x: c.x + 1, y: c.y, z: c.z, w: c.w},
		{x: c.x + 1, y: c.y - 1, z: c.z, w: c.w},
		{x: c.x, y: c.y + 1, z: c.z, w: c.w},
		// <-- original cell
		{x: c.x, y: c.y - 1, z: c.z, w: c.w},
		{x: c.x - 1, y: c.y + 1, z: c.z, w: c.w},
		{x: c.x - 1, y: c.y, z: c.z, w: c.w},
		{x: c.x - 1, y: c.y - 1, z: c.z, w: c.w},

		// below
		{x: c.x + 1, y: c.y + 1, z: c.z - 1, w: c.w},
		{x: c.x + 1, y: c.y, z: c.z - 1, w: c.w},
		{x: c.x + 1, y: c.y - 1, z: c.z - 1, w: c.w},
		{x: c.x, y: c.y + 1, z: c.z - 1, w: c.w},
		{x: c.x, y: c.y, z: c.z - 1, w: c.w},
		{x: c.x, y: c.y - 1, z: c.z - 1, w: c.w},
		{x: c.x - 1, y: c.y + 1, z: c.z - 1, w: c.w},
		{x: c.x - 1, y: c.y, z: c.z - 1, w: c.w},
		{x: c.x - 1, y: c.y - 1, z: c.z - 1, w: c.w},
	}...)

	return cells
}

func checkNeighbors(u universe, c cell) bool {
	sum := 0
	for _, c := range makeNeighborsList(c, u.hyper) {
		if u.cells[c] {
			sum = sum + 1
		}
	}
	if sum == 3 {
		return true
	} else if u.cells[c] && sum == 2 {
		return true
	}
	return false
}

func step(old universe) universe {
	new := universe{
		cells: make(map[cell]bool, len(old.cells)),
		hyper: old.hyper,
	}
	cellsToCheck := make([]cell, 0, len(old.cells)*80)
	for c := range old.cells {
		cellsToCheck = append(cellsToCheck, makeNeighborsList(c, old.hyper)...)
	}
	for _, c := range cellsToCheck {
		if checkNeighbors(old, c) {
			new.cells[c] = true
		}
	}
	return new
}

func newUniverse(input []string, hyper bool) universe {
	u := universe{
		cells: make(map[cell]bool, len(input)),
		hyper: hyper,
	}

	for i, r := range input {
		for j, c := range r {
			if c == '#' {
				u.cells[cell{z: 0, x: i, y: j, w: 0}] = true
			}
		}
	}

	return u
}

func countActivesInUniverse(u universe) {
	fmt.Println(len(u.cells))
}

func partOne() {
	f, _ := os.Open("input")
	reader := bufio.NewReader(f)
	scanner := bufio.NewScanner(reader)

	var input []string

	for scanner.Scan() {
		input = append(input, scanner.Text())
	}

	u := newUniverse(input, false)
	u = step(u)
	u = step(u)
	u = step(u)
	u = step(u)
	u = step(u)
	u = step(u)
	countActivesInUniverse(u)
}

func partTwo() {
	f, _ := os.Open("input")
	reader := bufio.NewReader(f)
	scanner := bufio.NewScanner(reader)

	var input []string
	for scanner.Scan() {
		input = append(input, scanner.Text())
	}

	u := newUniverse(input, true)
	u = step(u)
	u = step(u)
	u = step(u)
	u = step(u)
	u = step(u)
	u = step(u)
	countActivesInUniverse(u)
}