Detect whether sequence is a multiple of a subsequence in Python

Question

I have a tuple of zeros and ones, for instance:

(1, 0, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1)

It turns out:

(1, 0, 1, 1, 1, 0, 1, 1, 1,          


        

Answer 1

This one is just a dumb recursive comparison in Haskell. It takes about one second for Knoothe's million long string (f a). Cool problem! I'll think about it some more.

a = concat $ replicate 20000 
    [1,1,1,0,0,1,0,1,0,0,1,0,0,1,1,1,0,0,
     0,0,0,0,1,1,1,1,0,0,0,1,1,0,1,1,1,1,
     1,1,1,0,0,1,1,1,0,0,0,0,0,1]

f s = 
  f' s [] where
    f' [] result = []
    f' (x:xs) result =
      let y = result ++ [x]   
      in if concat (replicate (div (length s) (length y)) y) == s
            then y
            else f' xs y