[EMAIL PROTECTED] a écrit :
> Hi,
> I want to generate all non-empty substrings of a string of length >=2.
> Also,
> each substring is to be paired with 'string - substring' part and vice
> versa.
> Thus, ['abc'] gives me [['a', 'bc'], ['bc', 'a'], ['ab', 'c'], ['c',
> 'ab'], ['b', 'ac'], ['ac', 'b']] etc.
> Similarly, 'abcd' should give me [['a', 'bcd'], ['bcd', 'a'], ['abc',
> 'd'], ['d', 'abc'], ['b', 'acd'], ['acd', 'b'],['c', 'abd'], ['abd', 'c'],
> ['ab', 'cd'], ['cd', 'ab'], ['bc', 'ad'], ['ad', 'bc'], ['ac',
> 'bd'],['bd','ac']]
>
> I've tried the following but i cant prevent duplicates and i'm missing
> some substrings:
>
>
>>>>colocn = 'abcd'
>>>>k = 4
>>>>for i in range(k-1):
>
> for j in range(1,k):
> rule1 = [colocn[i:i+j],colocn[:i]+colocn[i+j:]]
> rule2 = [colocn[:i]+colocn[i+j:],colocn[i:i+j]]
> rules.append(rule1)
> rules.append(rule2)
>
>>>>rules
>
> [['a', 'bcd'], ['bcd', 'a'], ['ab', 'cd'], ['cd', 'ab'], ['abc', 'd'],
> ['d', 'abc'], ['b', 'acd'], ['acd', 'b'], ['bc', 'ad'], ['ad', 'bc'],
> ['bcd', 'a'], ['a', 'bcd'], ['c', 'abd'], ['abd', 'c'], ['cd', 'ab'],
> ['ab', 'cd'], ['cd', 'ab'], ['ab', 'cd']]
>
>
> Any ideas??
Algorithmic problem.
First, you need to get all permutations. This is a known algorithm, that
you'll find examples of on the net. Then for each permutation, list
possibles 'pair-splits'.
Here's a (probably sub-optimal, but it's getting late here) possible
implementation in functional style:
def rotate(lst):
yield lst
max = len(lst)
for i in range(1, max):
yield lst[i:] + lst[:-(max-i)]
def permute(lst):
if len(lst) > 2:
for rotated in rotate(lst):
head, tail = rotated[0], rotated[1:]
for permuted in permute(tail):
yield [head] + permuted
elif len(lst) == 2:
yield lst
yield lst[::-1]
else:
yield lst
def splits(lst):
for i in range(1, len(lst)):
yield lst[0:i], lst[i:]
def allsplits(lst):
for permuted in permute(lst):
for pair in splits(permuted):
yield pair
def listsubstrings(thestr):
format = lambda pair: (''.join(pair[0]), ''.join(pair[1]))
return [format(list(pair)) for pair in allsplits(list(thestr))]
print listsubstrings("abcd")
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