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day 8 part 2

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Thibaud Gasser 2023-12-08 14:24:07 +01:00
parent b6e553a61e
commit 446affa69f
1 changed files with 16 additions and 15 deletions
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day8/day8.py
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@ -1,4 +1,5 @@
import re import re
import math
from itertools import cycle from itertools import cycle
def parse_input(infile): def parse_input(infile):
@ -23,42 +24,42 @@ def part1(directions, nodes):
current_node = nodes[current_node][0] current_node = nodes[current_node][0]
else: else:
current_node = nodes[current_node][1] current_node = nodes[current_node][1]
print(f"Reached 'ZZZ' in {iterations} iterations") print(f"Part 1: reached 'ZZZ' in {iterations} iterations")
def part2(directions, nodes): def part2(directions, nodes):
current_nodes = [k for k in nodes.keys() if k.endswith("A")] current_nodes = [k for k in nodes.keys() if k.endswith("A")]
# keep track of iterations number for each visited node
# (the number will stop to beeing incremented once the node n_i value reached the target value 'xxZ')
iterations = [0] * len(current_nodes) iterations = [0] * len(current_nodes)
print(current_nodes, iterations)
for d in cycle(directions): for d in cycle(directions):
if all(c.endswith("Z") for c in current_nodes): if all(c.endswith("Z") for c in current_nodes):
break break
#iterations += len(current_nodes)
if d == "L": if d == "L":
new_nodes = [] new_nodes = []
for i, n in enumerate(current_nodes): for i, n in enumerate(current_nodes):
if not n.endswith("Z"): if n.endswith("Z"): # end condition already reached for this node
new_nodes.append(n)
else:
new_nodes.append(nodes[n][0]) new_nodes.append(nodes[n][0])
iterations[i] += 1 iterations[i] += 1
else:
new_nodes.append(n)
current_nodes = new_nodes current_nodes = new_nodes
#current_nodes = [c if c.endswith("Z") else nodes[c][0] for c in current_nodes]
else: else:
new_nodes = [] new_nodes = []
for i, n in enumerate(current_nodes): for i, n in enumerate(current_nodes):
if not n.endswith("Z"): if n.endswith("Z"): # end condition already reached for this node
new_nodes.append(n)
else:
new_nodes.append(nodes[n][1]) new_nodes.append(nodes[n][1])
iterations[i] += 1 iterations[i] += 1
else:
new_nodes.append(n)
current_nodes = new_nodes current_nodes = new_nodes
#current_nodes = [c if c.endswith("Z") else nodes[c][1] for c in current_nodes]
print(current_nodes, iterations) # the result is the lowest common multiple between the number of iterations
# for each node
result = math.lcm(*iterations)
print(f"Reached all nodes such that 'xxZ' in {iterations} iterations") print(f"Part 2: reached all nodes such that 'xxZ' in {result} iterations")
if __name__ == "__main__": if __name__ == "__main__":