- How many ways are there to cut a repeating string of “25” from a given string enumeration?
- Given a substring consisting of N consecutive 25’s, trigonometric number tri(N) is the number of pieces that can be cut from the substring.
- It would be faster to use (computer) regular expression to find out what’s going on, rather than looping through it yourself.
- Because I didn’t make it test-driven because I thought it would be easy, I forgot the specification that “if parentheses are used in a regular expression, findall will return only that range” and I WA’d.
(? : )is a non-capturing grouping python
import re
def tri(x):
return x * (x + 1) // 2
S = input()
ret = 0
print(sum(tri(len(s) // 2) for s in re.findall("(?:25)+", S)))
submitted #15126969 - dwango programming contest
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