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

from linked_lists import LinkedList, Cons, Nil

def del1_anyX(ys):
    if ys == Nil:
        return
    yield (ys.head, ys.tail)
    for (z, zs) in del1_anyX(ys.tail):
        yield (z, Cons(ys.head, zs))

def insert(x, ys):
    yield Cons(x, ys)
    if not ys == Nil:
        for zs in insert(x, ys.tail):
            yield Cons(ys.head, zs)

def append(xs, ys):
    if xs == Nil:
        return ys
    else:
        return Cons(xs.head, append(xs.tail, ys))

def append_anyXsYs(zs):
    yield ([], zs)
    if zs != Nil:
        for xs, ys in append_anyXsYs(zs.tail):
            yield (Cons(zs.head, xs), ys)

def perm1(xs):
    if xs == Nil:
        yield Nil
    else:
        for ys in perm1(xs.tail):
            for zs in insert(xs.head, ys):
                yield zs

def perm2(xs):
    if xs == Nil:
        yield Nil
    else:
        for y, ys in del1_anyX(xs):
            for zs in perm2(ys):
                yield Cons(y, zs)

def perm3(xs):
    if xs == Nil:
        yield Nil
    else:
        for ys, zs in append_anyXsYs(xs):
            if zs == Nil:
                continue
            qs = append(ys, zs.tail)
            for ws in perm3(qs):
                yield Cons(zs.head, ws)

# demonstracni vypis
if __name__ == "__main__":
    print("Prace se seznamy - permutace")
    print("-------------------------------\n")
    print("perm1 napsany pomoci insert")
    print("Vysledek volani perm1(LinkedList([1, 2, 3])): \n\t%s\n" % \
            list(perm1(LinkedList([1, 2, 3]))))

    print("perm2 napsany pomoci del1_anyX")
    print("Vysledek volani perm2(LinkedList([1, 2, 3])): \n\t%s\n" % \
            list(perm2(LinkedList([1, 2, 3]))))

    print("perm3 napsany pomoci deleni a spojovani seznamu")
    print("Vysledek volani perm3(LinkedList([1, 2, 3])): \n\t%s\n" % \
            list(perm3(LinkedList([1, 2, 3]))))

Prace se seznamy - permutace
-------------------------------

perm1 napsany pomoci insert
Vysledek volani perm1(LinkedList([1, 2, 3])): 
	[[1, 2, 3], [2, 1, 3], [2, 3, 1], [1, 3, 2], [3, 1, 2], [3, 2, 1]]

perm2 napsany pomoci del1_anyX
Vysledek volani perm2(LinkedList([1, 2, 3])): 
	[[1, 2, 3], [1, 3, 2], [2, 1, 3], [2, 3, 1], [3, 1, 2], [3, 2, 1]]

perm3 napsany pomoci deleni a spojovani seznamu
Vysledek volani perm3(LinkedList([1, 2, 3])): 
	[[1, 2, 3], [1, 3, 2], [2, 1, 3], [2, 3, 1], [3, 1, 2], [3, 2, 1]]