adventofcode/2016/day18/main.go

package main

import (
	"bytes"
	"fmt"
	"os"

	h "git.bullercodeworks.com/brian/adventofcode/helpers"
)

func main() {
	if len(os.Args) < 3 {
		fmt.Println("Usage: ./day18 <filename> <numrows>")
	}
	input := h.FileToBytes(os.Args[1])
	numRows := h.Atoi(os.Args[2])

	room := [][]byte{input}
	for row := 1; row < numRows; row++ {
		room = append(room, []byte{})
		for tile := 0; tile < len(room[0])-1; tile++ {
			var l, r byte
			switch tile {
			case 0:
				l, r = '.', room[row-1][tile+1]
			case len(input) - 2:
				l, r = room[row-1][tile-1], '.'
			default:
				l, r = room[row-1][tile-1], room[row-1][tile+1]
			}
			if l != r && (l == '^' || r == '^') {
				room[row] = append(room[row], '^')
			} else {
				room[row] = append(room[row], '.')
			}
		}
	}
	var safeCount int
	for i := range room {
		safeCount += bytes.Count(room[i], []byte{'.'})
	}
	fmt.Println(safeCount, "safe tiles")
}