Day 18 Complete

2016/day18/input

@@ -0,0 +1 @@
+^.^^^..^^...^.^..^^^^^.....^...^^^..^^^^.^^.^^^^^^^^.^^.^^^^...^^...^^^^.^.^..^^..^..^.^^.^.^.......

2016/day18/main.go

@@ -0,0 +1,43 @@
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"os"
+
+	"../../"
+)
+
+func main() {
+	if len(os.Args) < 3 {
+		fmt.Println("Usage: ./day18 <filename> <numrows>")
+	}
+	input := aoc.FileToBytes(os.Args[1])
+	numRows := aoc.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")
+}