From 08f7db87ad8f3c27ad6e78f3b4a8f811a9a94f46 Mon Sep 17 00:00:00 2001
From: Meutel <meutel@meutel.net>
Date: Sun, 3 Dec 2017 12:19:25 +0100
Subject: [PATCH] Day 3: spiral

---
 03dec/main.go | 95 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 95 insertions(+)
 create mode 100644 03dec/main.go

diff --git a/03dec/main.go b/03dec/main.go
new file mode 100644
index 0000000..e419885
--- /dev/null
+++ b/03dec/main.go
@@ -0,0 +1,95 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"strconv"
+)
+
+const (
+	W = iota
+	N
+	E
+	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 {
+		os.Exit(1)
+	}
+	fmt.Println(n)
+
+	// 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
+}