Generate all possible strings from a list of token

Question

Hi I have a list of tokens, like:

hel
lo
bye

and i want to generate all the possible combinations of such strings, like:

hello
lohel
helbye
byehel
lobye
byelo

Language is not important, any advice?

I found http://stackoverflow.com/questions/3846123/generating-permutations-using-bash, but this makes permutation on a single line.

Answer 1

Update: I see I wasn't explicit enough.

Haskell has a permutations function that would help:

import Data.List
permutations ["hel","lo","bye"] ==
[["hel","lo","bye"],["lo","hel","bye"],["bye","lo","hel"],
 ["lo","bye","hel"],["bye","hel","lo"],["hel","bye","lo"]]

If you want each permutation concatenated, use

map concat (permutations ["hel","lo","bye"]) ==
["hellobye","lohelbye","byelohel","lobyehel","byehello","helbyelo"]

If you actually want combinations of two substrings (like your example output) instead of all permutations of substrings, as @Sven noticed, use the Math.Combinatorics.Graph module and:

map concat (combinationsOf 2 ["hel","lo","bye"])

That matches your example data in some respects but not others. I could go on to speculate that you want "all possible strings" as the title says, or all permutations of two-token subsets, or what have you, but it's kind of pointless to speculate since you've already accepted an answer.

Answer 2

itertools.permutations can do that for you.

>>> l = ['hel', 'lo', 'bye']
>>> list(itertools.permutations(l, 2))
[('hel', 'lo'), ('hel', 'bye'), ('lo', 'hel'), ('lo', 'bye'), ('bye', 'hel'), ('bye', 'lo')]

Or if you want combinations, you can use itertools.combinations.

>>> l = ['hel', 'lo', 'bye']
>>> list(itertools.combinations(l, 2))
[('hel', 'lo'), ('hel', 'bye'), ('lo', 'bye')]

Answer 3

Your example can be written in Python as

from itertools import combinations
print list(combinations(["hel", "lo", "bye"], 2))

To combine the output to strings again:

print ["".join(a) for a in combinations(["hel", "lo", "bye"], 2)]

If you interested in the actual implementation of this function, have a look at the documentation.

Answer 4

a = ['hel', 'lo', 'bye']
print '\n'.join(''.join(x) for x in itertools.permutations(a, 2))

Answer 5

Easy in python with itertools.

Here is the token permutation example:

import itertools

tokens = ["hel", "lo", "bye"]

for i in range(1, len(tokens) + 1):
    for p in itertools.permutations(tokens, i):
        print "".join(p)

Alternatively, this treats each character as a token:

import itertools

tokens = ["hel", "lo", "bye"]

chars = "".join(tokens)
for i in range(1, len(chars) + 1):
    for p in itertools.permutations(chars, i):
        print "".join(p)

Answer 6

Python has a permutations too. :)

Answer 7

Given that other languages are acceptable:

#!/usr/bin/perl

use strict; use warnings;
use Algorithm::Combinatorics qw(permutations);

my $data = [ qw( hel lo bye ) ];
my $it = permutations($data);

while ( my $p = $it->next ) {
    print @$p, "\n";
}

hellobye
helbyelo
lohelbye
lobyehel
byehello
byelohel

Answer 8

Looks like you want permutations:

from itertools import permutations

# easy way to make a list for words
words = 'hel lo bye'.split()

# fetch two-word permutations, joined into a string
for word in [''.join(s) for s in permutations(words,2)]:
    print word

Output:

hello
helbye
lohel
lobye
byehel
byelo