aoc 2017 (day 1-6)

www/statics/aoc/2017/03_solution-2.py

@@ -0,0 +1,53 @@
+#!/usr/bin/env python3
+
+import aoc
+import math
+import itertools
+
+
+# https://stackoverflow.com/questions/10094745
+def spiralpos(n):
+    k = math.ceil((math.sqrt(n) - 1) / 2)
+    t = 2 * k + 1
+    m = t ** 2
+
+    t -= 1
+
+    if n >= m - t:
+        return k - (m - n), -k
+
+    m -= t
+
+    if n >= m - t:
+        return -k, -k + (m - n)
+
+    m -= t
+
+    if n >= m - t:
+        return -k + (m - n), k
+
+    return k, k - (m - n - t)
+
+
+rawinput = aoc.read_input(3)
+intinput = int(rawinput)
+
+dirs = [
+    (-1, -1), (00, -1), (+1, -1),
+    (-1, 00),           (+1, 00),
+    (-1, +1), (00, +1), (+1, +1),
+]
+
+grid = dict()
+grid[(0, 0)] = 1
+
+for i in itertools.count(2):
+    x, y = spiralpos(i)
+    v = 0
+    for dx, dy in dirs:
+        if (x + dx, y + dy) in grid:
+            v += grid[(x + dx, y + dy)]
+    if v > intinput:
+        print(v)
+        exit()
+    grid[(x, y)] = v