#!/usr/bin/env python

# https://adventofcode.com/2025/day/11

f = open("day11input.txt", "r")
#f = open("testinput.txt", "r")

graph = {}
for line in f.readlines():
  node, outputs = line.strip("\n").split(":")
  graph[node] = outputs.strip().split(" ")


def part1(current_path: list[str] | str, end: str) -> None:
  if isinstance(current_path, str):
    current_path = [current_path]
  
  node = current_path[-1]

  # check for dead ends
  if node not in graph.keys():
    return

  # check if end node is reachable from current node
  if end in graph[node]:
    found_paths.append(current_path + [end])
    return
  
  # check all outputs
  for output in graph[node]:
    # avoid loops
    if output in current_path:
      continue
    part1(current_path + [output], end)
        


def part2(start: str, end: str) -> int:
  print(f"STARTING BACKWARDS SEARCH FROM {end} TO {start}")
  num_paths = {end: 0}

  def backsearch(target_node: str, current_node: str) -> int:
    # init num_paths value for current node
    num_paths[current_node] = 0

    # find nodes with edges into current node
    inputs = list(filter(lambda n: current_node in graph[n], graph.keys()))

    # check if current_node is a dead end
    if len(inputs) == 0:
      return
    
    # loop over input nodes
    for node in inputs:
      # check if node is the target node
      if node == target_node:
        num_paths[current_node] = 1

      # input node was visited already
      elif node in num_paths.keys():
        num_paths[current_node] += num_paths[node]

      # input node was not yet visited
      else:
        backsearch(target_node, node)
        num_paths[current_node] += num_paths[node]
      
    return

  backsearch(start, end)
  return num_paths[end]
  



# part 1
found_paths = []
part1("you", "out")
print(len(found_paths))

# part2
svr2dac = part2("svr", "dac")
print(svr2dac)
dac2fft = part2("dac", "fft")
print(dac2fft)
fft2out = part2("fft", "out")
print(fft2out)
svr2fft = part2("svr", "fft")
print(svr2fft)
fft2dac = part2("fft", "dac")
print(fft2dac)
dac2out = part2("dac", "out")
print(dac2out)

print("final result:", svr2dac * dac2fft * fft2out + svr2fft * fft2dac * dac2out)