AS challenge from IEEE2013

as.py

#!/usr/bin/python3 
import collections

def find_new_paths(graph, destination, current_paths, closed_paths):
    new_paths = []
    for path in current_paths:
        last_element = path[-1]
        for next_element in graph[last_element]:
            new_path = list(path)
            new_path.append(next_element)
            if next_element == destination:
                closed_paths.append(new_path)
            else:
                new_paths.append(new_path)

    return new_paths, closed_paths


nodes = collections.defaultdict(list)
destination = input().strip()

while True:
    inp = input()
    if inp == 'A A':
        break
    # Todo: check if the characters are between F and Z
    nodes[inp[0]].append(inp[2])


opened_paths = [['F']]
closed_paths = []

for i in range(len(nodes)):
    opened_paths, closed_paths = find_new_paths(nodes, destination, opened_paths, closed_paths)


if(closed_paths):
    shortest = min([len(x) for x in closed_paths])
    shortest_paths_in_strings = sorted([' '.join(x) for x in closed_paths if len(x) == shortest])
    
    print('Total Routes: %s' % len(closed_paths) )
    print('Shortest Route Length: %s' % shortest)
    print('Shortest Route after Sorting of Routes of length %s: %s' % (shortest, shortest_paths_in_strings[0]))
else:
    print('No Route Available from F to %s' % destination)