Day 3: spiral

03dec/main.go

@@ -13,6 +13,17 @@ const (
 	S
 )
 
+var (
+	cur  int
+	x    int
+	y    int
+	dir  int
+	xmax int
+	xmin int
+	ymax int
+	ymin int
+)
+
 func main() {
 	n, err := strconv.Atoi(os.Args[1])
 	if err != nil {
@@ -20,6 +31,65 @@ func main() {
 	}
 	fmt.Println(n)
 
-	cur, x, y, dir, width, height := 1, 0, 0, W
 	// create cell and compute change direction, expand grid
+	for cur < n {
+		nextMove()
+		fmt.Println(cur, x, y)
+	}
+
+	fmt.Println("\n", Abs(x)+Abs(y))
+}
+
+func nextMove() {
+	if cur == 0 {
+		dir = S
+	} else {
+		x1, y1 := dirMove()
+		if outOfBound(x1, y1) {
+			changeDir()
+			x1, y1 = dirMove()
+		}
+		x, y = x1, y1
+	}
+	cur++
+}
+
+func dirMove() (int, int) {
+	switch dir {
+	case W:
+		return x - 1, y
+	case N:
+		return x, y + 1
+	case E:
+		return x + 1, y
+	case S:
+		return x, y - 1
+	default:
+		return x, y
+	}
+}
+func outOfBound(x1 int, y1 int) bool {
+	return x1 > xmax || x1 < xmin || y1 > ymax || y1 < ymin
+}
+func changeDir() {
+	switch dir {
+	case W:
+		dir = S
+		ymin--
+	case N:
+		dir = W
+		xmin--
+	case E:
+		dir = N
+		ymax++
+	case S:
+		dir = E
+		xmax++
+	}
+}
+func Abs(n int) int {
+	if n < 0 {
+		return -n
+	}
+	return n
 }