2017 Day 3

2017/day3.py

@@ -0,0 +1,46 @@
+input = 312051
+import numpy as np
+
+num_rings = 1000
+rings_sizes = np.empty(num_rings, dtype=np.int64)
+
+rings_sizes[0] = 1
+for i in range(1, num_rings):
+  rings_sizes[i] = 8*i
+
+rings_ends = rings_sizes.cumsum()
+
+def find_position(number):
+  ring_idx = (rings_ends >= number).argmax()
+  pos_on_ring = number - rings_ends[ring_idx-1] if ring_idx > 0 else 1
+  return ring_idx, pos_on_ring
+
+def distance(number):
+  ring_idx, pos_on_ring = find_position(number)
+  ring_pos_dist = abs(pos_on_ring%(ring_idx*2)-ring_idx)
+  return ring_idx + ring_pos_dist
+
+print(distance(input))  # Part 1
+
+
+mem_plane_rings = 20
+mp_offset = mem_plane_rings
+mp_size = mem_plane_rings*2+1
+mem_plane = np.zeros((mp_size, mp_size), dtype=np.int64)
+
+directions = np.array([[0,1], [-1,0], [0,-1], [1,0]], dtype=np.int32)
+direction = -1
+position = np.array((mp_offset, mp_offset), dtype=np.int32)
+mem_plane[mp_offset, mp_offset] = 1
+for i in range((mp_size-2)**2):
+  if mem_plane[tuple(position + directions[(direction+1)%4])] == 0:
+    direction = (direction+1) % 4
+  position += directions[direction]
+  x, y = position
+  mem_plane[x,y] = mem_plane[x-1:x+2, y-1:y+2].sum()
+  if mem_plane[x,y] > input:
+    print(mem_plane[x,y])  # Part 2
+    break
+
+
+