#!/usr/bin/env python3
from pathlib import Path
from collections import deque


def process_node(node, available_edges, visited):
    paths = deque()
    if node == "end":
        paths.append(deque(node))
        return paths
    if node.islower():
        visited.add(node)
    neighbors = [n for e in available_edges if node in e for n in e if n != node]
    for n in neighbors:
        if n not in visited:
            nxt = process_node(n, available_edges, visited)
            for p in nxt:
                p.appendleft(node)
            paths += nxt
    if node in visited:
        visited.remove(node)
    return paths


def process_node_twice(node, available_edges, visited, visited_twice):
    num_paths = 0
    if node == "end":
        return 1
    if node.islower():
        if node in visited and visited_twice:
            return num_paths
        elif node in visited and node != "start":
            visited_twice = node
        else:
            visited.add(node)
    neighbors = [n for e in available_edges if node in e for n in e if n != node]
    for n in neighbors:
        if n not in visited or visited_twice != node and n != "start":
            num_paths += process_node_twice(n, available_edges, visited, visited_twice)
    if visited_twice == node:
        visited_twice = None
    elif node in visited:
        visited.remove(node)
    return num_paths


def part_1(input):
    result = 0
    edges = []
    for line in input:
        n_start, n_end = line.strip().split('-')
        e = (n_start, n_end)
        edges.append(e)
    paths = process_node("start", edges, set())
    result = len(paths)
    print("Part 1 result:", result)


def part_2(input):
    result = 0
    edges = []
    for line in input:
        n_start, n_end = line.strip().split('-')
        e = (n_start, n_end)
        edges.append(e)
    result = process_node_twice("start", edges, set(), None)
    print("Part 2 result:", result)


input = list()
p = Path(__file__).with_name('input.txt')
with open(p) as f:
    input = f.readlines()
    part_1(input)
    part_2(input)