% nacteni:
/* ['3.6_17.pl']. */

solution(Start ,Solution) :- breadth_first_search([[ Start ]], Solution).

breadth_first_search([[ Node|Path]|_],[Node|Path]) :- goal(Node).
breadth_first_search([[ N|Path]|Paths],Solution) :-
    bagof([M,N|Path],(move(N,M),\+ member(M,[N|Path])), NewPaths),
    NewPaths\=[], append(Paths,NewPaths,Path1), !,
    breadth_first_search(Path1,Solution); breadth_first_search(Paths,Solution).

% vzorova data
goal(e).
move(a,b). move(a,e). move(a,f).
move(b,c). move(f,c). move(c,d). move(d,e).

% demonstracni vypis

start:- 
    write('breadth_first_search'),nl,
    write('Prvni reseni solution(a,Solution):'),nl,
    solution(a,Solution),write(Solution),nl.
?-start.

breadth_first_search
Prvni reseni solution(a,Solution):
[e,a]

#!/usr/bin/env python
# encoding=utf-8 (pep 0263)

from linked_lists import LinkedList, Cons, Nil, member, append

def is_goal(x):
    # zavisi na resenem problemu
    return x == "E"

def solution(node):
    for path in breadth_first_search(LinkedList([LinkedList(node)])):
        yield path

def breadth_first_search(paths):
    if paths == Nil:
        return
    path = paths.head
    node = path.head
    if is_goal(node):
        yield path
    new_paths = Nil
    for node1 in move_anyY(node):
        if not member(node1, path):
            new_paths = Cons(Cons(node1, path), new_paths)
    if new_paths != Nil:
        paths1 = append(paths.tail, new_paths)
    else:
        paths1 = paths.tail
    for path in breadth_first_search(paths1):
        yield path

graph = dict(A=["B", "E", "F"],
             B=["C"], F=["C"],
             C=["D"],
             D=["E"])

def move_anyY(x):
    # zavisi na resenem problemu
    if x in graph:
        for y in graph[x]:
            yield y

# demonstracni vypis
if __name__ == "__main__":
    print("Breadth-First Search")
    print("Volani next(solution('A')): %s" % next(solution('A')))
    print("Vsechna reseni solution('A'):")
    for s in solution('A'):
        print s

Breadth-First Search
Volani next(solution('A')): ['E', 'A']
Vsechna reseni solution('A'):
['E', 'A']
['E', 'D', 'C', 'F', 'A']
['E', 'D', 'C', 'B', 'A']