This is a Python implementation of the QuickPerm algorithm described by Phillip Paul Fuchs at http://www.quickperm.org that generates all permutations of a list without using recursion

quickperm.py

#!/usr/bin/env python

#
# This is a Python implementation of the QuickPerm algorithm described by Phillip Paul Fuchs at http://www.quickperm.org 
# that generates all permutations of a list without using recursion.
#

a = ['a', 'b', 'c', 'd']

N = len(a)
p = range(0, N + 1)
i = 1
print a	
while i < N:
	p[i] -= 1
	if i % 2 == 1:
		j = p[i]
	else:
		j = 0
	a[j], a[i] = a[i], a[j]
	print a
	i = 1
	while p[i] == 0:
		p[i] = i
		i += 1

thanks pretty epic bro legit 😎

A little modification which use only single yield (instead of two prints), so that no duplicated inline codes and look nicer to me.

def quickperm(a):
    N = len(a)
    p = [*range(N+1)]
    i = 1
    while True:
        yield a
        if i >= N: break

        p[i] -= 1
        j = 0 if i % 2 == 0 else p[i]
        a[j], a[i] = a[i], a[j]

        i = 1
        while p[i] == 0:
            p[i] = i
            i += 1

does anyone have a parallel version of this, eg. using 2 or more cores ?