How can I generate a list of all possible permutat

问题:

This question already has an answer here:

• How to generate all permutations of a list in Python 29 answers
• Randomize a string input into all possibilities 1 answer

So I am making a word generator that takes several inputted letters, puts them in all possible positions, and matches them with a document to find words. If I am approaching this wrong please tell me! If not how can I do this? Thanks

回答1:

to generate all permutations of a given list of letters, use the itertools module.

import itertools 
for word in itertools.permutations( list_of_letters ):
   print ''.join(word)

回答2:

It might be faster to run it in reverse: index your document, and for each word, see if it is a subset of your list of letters.

回答3:

You can write your own function (:

def permutation(head, tail=''):
    if len(head) == 0: 
        print tail
    else:
        for i in range(len(head)):
            permutation(head[0:i] + head[i + 1:], tail + head[i])

回答4:

def allpermutationsOfString(words):
  if len(words) == 1:
    return [words]
  result = []
  for index, letter in enumerate(words):
    wordWithoutLetter = words[:index] + words[index+1:]
    result = result + [letter + word for word in allpermutationsOfString(wordWithoutLetter)]
  return result

print allpermutationsOfString("watup") #will print all permutations of watup

Here's another way to implement the algorithm.