day18: solved part 1

Author: fxnn

Diff for: day18/main.go

@@ -12,32 +12,36 @@ import (
 
 const (
 	CORRUPTED = -1
+	UNIVSITED = 0
 )
 
 func printSpace(space [][]int) {
+	var max = len(space) - 1
 	for y := range space {
 		for x := range space[y] {
-			fmt.Printf("%2d ", space[y][x])
+			switch space[y][x] {
+			case CORRUPTED:
+				fmt.Print(" C")
+			case UNIVSITED:
+				fmt.Print(" .")
+			default:
+				fmt.Printf("%2d", space[y][x])
+			}
+			if max > 9 {
+				fmt.Print(" ")
+			}
 		}
 		fmt.Println()
 	}
 	fmt.Println()
 }
 
-func main() {
-	var size = flag.Int("max", 70, "coordinates have range [0,max]")
-	var count = flag.Int("count", 1024, "number of bytes that have fallen")
-	flag.Parse()
-	var space = make([][]int, *size+1)
-	for y := range space {
-		space[y] = make([]int, *size+1)
-	}
-
+func readSpace(space [][]int, count int) {
 	var scanner = bufio.NewScanner(os.Stdin)
 	var pattern = regexp.MustCompile(`^(\d+),(\d+)$`)
 
 	var fallen int
-	for scanner.Scan() && fallen < *count {
+	for scanner.Scan() && fallen < count {
 		var line = scanner.Text()
 		var matches = pattern.FindStringSubmatch(line)
 		var x, y int
@@ -52,6 +56,60 @@ func main() {
 		fmt.Fprintf(os.Stderr, "Error: %s\n", err)
 		os.Exit(1)
 	}
+}
 
+func makeSpace(size int) [][]int {
+	var space = make([][]int, size+1)
+	for y := range space {
+		space[y] = make([]int, size+1)
+	}
+	return space
+}
+
+var directions = []util.Point{{X: -1, Y: 0}, {X: 1, Y: 0}, {X: 0, Y: 1}, {X: 0, Y: -1}}
+
+func markAround(from util.Point, space [][]int, set []util.Point) []util.Point {
+	var size = len(space)
+	var steps = space[from.Y][from.X]
+	for _, direction := range directions {
+		var to = from.Add(direction)
+		if to.IsInBounds(size, size) && space[to.Y][to.X] == 0 {
+			set = append(set, to)
+			space[to.Y][to.X] = steps + 1
+		}
+	}
+	return set
+}
+
+func expandSet(set []util.Point, space [][]int) []util.Point {
+	var newset = []util.Point{}
+	for _, point := range set {
+		newset = markAround(point, space, newset)
+	}
+	return newset
+}
+
+func searchPath(space [][]int) int {
+	var max = len(space) - 1
+	var set []util.Point = []util.Point{{X: 0, Y: 0}}
+
+	space[0][0] = 1
+	for space[max][max] == 0 && len(set) > 0 {
+		set = expandSet(set, space)
+	}
+
+	return space[max][max]
+}
+
+func main() {
+	var max = flag.Int("max", 70, "coordinates have range [0,max]")
+	var count = flag.Int("count", 1024, "number of bytes that have fallen")
+	flag.Parse()
+
+	var space = makeSpace(*max)
+	readSpace(space, *count)
+	printSpace(space)
+	var steps = searchPath(space) - 1
+	fmt.Printf("found exit in %d steps\n", steps)
 	printSpace(space)
 }