#!/usr/local/bin/python3
# Author: Dr. Robert Heckendorn, Computer Science Department, University of Idaho, 2013
from lib import *

def reverse(x, a, b) :
    while b>a :
        (x[a], x[b]) = (x[b], x[a])
        a+=1
        b-=1

def perm(size) :
    x = list(range(0, size))
    while True :
        print(x)   # print permutation

        done = True
        for i in range(size-2, -1, -1) :
            if x[i]<x[i+1] :  # find first decreasing value from right
                done = False
                break
        # we know that from x[i+1]...x[size-1] is decreasing in size

        # done if 
        if done : break

        for j in range(size-1, 0, -1) :
            if x[j]>x[i] :
                break
        # finds the largest j such that x[j]>x[i]
        # we know that x[j]>x[i]>x[j-1] that is this is the place to insert x[i]
        # in the ordered suffix.   

        # So insert it there
        (x[i], x[j]) = (x[j], x[i])

        # produce the next lexigraphically minimum list
        reverse(x, i+1, size-1)
    
perm(6)