Permutation without repetition

Question

I am searching for a simple command/function to generate permutation of a numbers set given as a parameters of a shell command.

Here on example I can generate all 6-number permutations from 1-6 numbers in Python:

root@debian:~# python
Python 2.7.13 (default, Sep 26 2018, 18:42:22)
[GCC 6.3.0 20170516] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from itertools import permutations
>>> perm = permutations([1, 2, 3, 4, 5, 6], 6)
>>> for i in list(perm):
...     print i
...
(1, 2, 3, 4, 5, 6)
(1, 2, 3, 4, 6, 5)
(1, 2, 3, 5, 4, 6)
(1, 2, 3, 5, 6, 4)
(1, 2, 3, 6, 4, 5)
(1, 2, 3, 6, 5, 4)
(1, 2, 4, 3, 5, 6)
[...]

How do do it in a simpler way, best with an one-liner command where all such numbers as an arguments can be provided, for example:

$ command 1 2 3 4 5 6

with output expected as:

1 2 3 4 5 6
1 2 3 4 6 5
1 2 3 5 4 6
1 2 3 5 6 4
1 2 3 6 4 5
1 2 3 6 5 4
1 2 4 3 5 6
[...]

Update: Only one line is printed out with when script uses arguments:

root@debian:~# cat permut.py
import sys
n1 = sys.argv[1]
n2 = sys.argv[2]
n3 = sys.argv[3]
n4 = sys.argv[4]
n5 = sys.argv[5]
n6 = sys.argv[6]
from itertools import combinations
comb = combinations([sys.argv[1], n2, n3, n4, n5, n6], 6)
for i in list(comb):
        print i
root@debian:~# python permut.py 1 2 3 4 5 6
('1', '2', '3', '4', '5', '6')
root@debian:~#

While when numbers are provided in the scipt it works good, why?

root@debian:~# cat permut2.py
from itertools import permutations
perm = permutations([21, 2, 30, 34, 15, 46], 6)
for i in list(perm):
        print i
root@debian:~# python permut2.py|head -10
(21, 2, 30, 34, 15, 46)
(21, 2, 30, 34, 46, 15)
(21, 2, 30, 15, 34, 46)
(21, 2, 30, 15, 46, 34)
(21, 2, 30, 46, 34, 15)
(21, 2, 30, 46, 15, 34)
(21, 2, 34, 30, 15, 46)
(21, 2, 34, 30, 46, 15)
(21, 2, 34, 15, 30, 46)
(21, 2, 34, 15, 46, 30)

Also with "int(sys.argv)" does not work:

root@debian:~# cat permut.py
import sys
n1 = int(sys.argv[1])
n2 = int(sys.argv[2])
n3 = int(sys.argv[3])
n4 = int(sys.argv[4])
n5 = int(sys.argv[5])
n6 = int(sys.argv[6])
from itertools import combinations
comb = combinations([n1, n2, n3, n4, n5, n6], 6)
for i in list(comb):
        print i
root@debian:~# python permut.py 1 2 3 4 5 6
(1, 2, 3, 4, 5, 6)
root@debian:~#

You can also turn your Python commands into a Python script, and use that as `command`. — 9769953, Mar 28 '20 at 11:31
I am voting to reopen as the question I myself selected does not actually give an answer to this, which asks for a one-liner. I have written such a simple one-liner that I'd like to share here. — Enlico, Mar 28 '20 at 12:01
I showed python code as the only option I found for my case, I am not a python programmer and was expecting something simpler, even using a bash. The proposed url does not answer my question at all (completely different case and input). — Chris, Mar 28 '20 at 12:10
I have the onliner, however: `echo {1..6}{1..6}{1..6}{1..6}{1..6}{1..6} | sed -E 's/[^ ]*([0-9])[0-9]*\1[^ ]*( |$)//g'`. If they reopen the question, I'll post it as an answer. — Enlico, Mar 28 '20 at 12:44
The onliner in previous command does not support other cases, any set of 6 numbers, for example permutation without repetition of 12, 4, 43, 30, 65, 23 — Chris, Mar 28 '20 at 12:58
It supports only one digit-numbers. `sed` has not builtin arithmetic capabilities, so there's no one-line way to make it work with any numbers. — Enlico, Mar 28 '20 at 13:17
Any hint to the update I added to the ticker? Why python with args does not work well? — Chris, Mar 28 '20 at 13:20
Let us [continue this discussion in chat](https://chat.stackoverflow.com/rooms/210492/discussion-between-enrico-maria-de-angelis-and-chris). — Enlico, Mar 28 '20 at 15:16

score 1 · Accepted Answer · answered Mar 28 '20 at 13:30

1

Take the list of command line parameters and for each permutation of this list display individual values separated with spaces.

import itertools
import sys

for p in itertools.permutations(sys.argv[1:]):
    print(" ".join(p))

answered Mar 28 '20 at 13:30

dlask

8,776
1
26
30

Enlico · Answer 2 · 2020-03-28T15:59:04.473

Update

The following oneliner does what the OP asks.

echo {12,4,43,30}","{12,4,43,30}","{12,4,43,30}","{12,4,43,30} | sed -E 's/\<([0-9]+,)*([0-9]+),([0-9]+,)*\2(,[0-9]+)*\>( |$)//g;s/ +/\n/g'

It works like this:

the echo command generates the nⁿ space-separated permutations separating the numbers of each permutation by commas;
- (clearly any way of generating this is fine, as the tricky part is discarding the permutations which have repetitions.)
the sed command
1. makes the magic with one substitution
2. puts each permutation on a line with the second substitution s/ +/\n/g.

Original answer

The following oneliner works for the original answer, which used only single digit-numbers:

echo {1..6}{1..6}{1..6}{1..6}{1..6}{1..6} | sed -E 's/[^ ]*([0-9])[0-9]*\1[^ ]*( |$)//g'

I don't doubt it might be successfully adapted to work with multiple digit numbers, but at the moment I have no idea.

Permutation without repetition

2 Answers2

Update

Original answer