Rep-string
Rep-string is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.
Given a series of ones and zeroes in a string, define a repeated string as a string which is created by repeating a substring of the first N characters of the string two or more times, truncated on the right to the length of the input string.
For example, the string '10011001100'
is a repeated string as the leftmost four characters of '1001'
are repeated three times and truncated on the right to give the original string.
The task is to:
- Write a function/subroutine/method/... that takes a string and returns an indication of if it is a repeated string and the repeated string. (Either the string that is repeated, or the number of repeated characters would suffice).
- Use the function to indicate the repeating substring if any, in the following
'1001110011' '1110111011' '0010010010' '1010101010' '1111111111' '0100101101' '0100100' '101' '1'
- Show your output on this page.
Python
<lang python>def is_repeated(text):
'check if the first part of the string is repeated throughout the string' len_text = len(text) for rep_len in range(len_text // 2, 0, -1): reps = (len_text + rep_len) // rep_len if (text[:rep_len] * reps).startswith(text): return rep_len # equivalent to boolean True as will not be zero return 0 # equivalent to boolean False
matchstr = """\ 1001110011 1110111011 0010010010 1010101010 1111111111 0100101101 0100100 101 1 """ for line in matchstr.split():
ln = is_repeated(line) print('%r has a repetition length of %i i.e. %s' % (line, ln, repr(line[:ln]) if ln else '*not* a repeated string'))</lang>
- Output:
'1001110011' has a repetition length of 5 i.e. '10011' '1110111011' has a repetition length of 4 i.e. '1110' '0010010010' has a repetition length of 3 i.e. '001' '1010101010' has a repetition length of 4 i.e. '1010' '1111111111' has a repetition length of 5 i.e. '11111' '0100101101' has a repetition length of 0 i.e. *not* a repeated string '0100100' has a repetition length of 3 i.e. '010' '101' has a repetition length of 0 i.e. *not* a repeated string '1' has a repetition length of 0 i.e. *not* a repeated string