List all permutations.

#! /usr/bin/python
import sys, new

#prepare
class lst(list):
    def swap(self, i, j):
        self[i], self[j] = self[j], self[i]
    def reverseFrom(self, at):
        x = at + (len(self)-at)/2
        j = len(self)-1
        for i in xrange(at, x):
            self.swap(i, j)
            j -= 1


arr, n = lst(), int(sys.argv[1])
for i in xrange(n):
    arr.append(i+1)

#permutation
def nextPerm(seq):
    i = len(seq) - 2
    while seq[i] > seq[i+1]:    #search 'jump' when next element is lesser
        i -= 1          #(searching from end, but it isn't matter)
        if i < 0:
            break       #no jump - permutation lexicographic maximal
    if i >= 0:
        j = len(seq) - 1
        while seq[i] > seq[j]:  #search larger element then el. on our 'jump'
            j -= 1
        seq.swap(i, j)      #swap them
        seq.reverseFrom(i+1)    #reverse 'tail' - all elements after earlier 'jump'
        return True #return true if exist next lexicographic permutation
    seq.reverseFrom(0)      #reverse all sequence becouse it's maximal
    return False #return false if next permutation is lexicographic minimal

#print all permutations
do, i = True, 0
while do:
    sys.stdout.write(str(i) + ')\t' + str(arr) + '\n') #just print
    i += 1
    do = nextPerm(arr)  #compute next permutation of sequence and get
                #boolean - is one the largest?
print 'last:\t', arr