Day 13

13.py

@@ -0,0 +1,27 @@
+#!/usr/bin/python3
+
+import itertools
+
+input = 1364
+
+high = lambda x: sum([1 for d in bin(x) if d == '1'])
+wall = lambda x, y: high(x*x + 3*x + 2*x*y + y + y*y + input) % 2 == 1
+all_moves = lambda x, y: [(x-1, y), (x+1, y), (x, y-1), (x, y+1)]
+moves = lambda x, y: (m for m in all_moves(x, y) if m[0] >= 0 and m[1] >= 0 and not wall(*m))
+queue = set([(1, 1)])
+visited = set()
+distance = {}
+steps = 0
+
+while steps < 100:
+	for c in queue:
+		if c not in distance:
+			distance[c] = steps
+
+	visited = visited.union(queue)
+	next_queue = set(itertools.chain.from_iterable(moves(*c) for c in queue)) - visited
+	queue = next_queue
+	steps += 1
+
+print("Part 1: %s" % distance[(31, 39)])
+print("Part 2: %s" % sum(1 for s in distance.values() if s <= 50))