"""
Térinformatikai algoritmusok
Gráfok ábrázolási formái és bejárásai
Máté Cserép <mcserep@inf.elte.hu>
"""

import csv
import networkx as nx # pip3 install networkx

# Read user input
start_city = input('Start city: ')
transfer_number = int(input('Number of transfers: '))

graph = nx.Graph() # undirected graph
# use nx.DiGraph() for directed graphs

# Read CSV file and construct graph
with open('flights.csv') as csv_file:
    csv_reader = csv.reader(csv_file, delimiter=';')
    for row in csv_reader:
        #print('Reading flight {0} <=> {1}'.format(row[0], row[1]))
        graph.add_edge(row[0], row[1])

# Check existance of start city
if graph.has_node(start_city):
    reachable_cities = [ start_city ]

    # Do breadth first search
    successors = nx.bfs_successors(graph, start_city, transfer_number)
    for item in successors:
        print('{0} -> {1}'.format(item[0], item[1]))
        reachable_cities += item[1]

    print('Reachable cities: {0}'.format(reachable_cities))
else:
    print('{0} city is unknown'.format(start_city))