1790. Oulipo

The French author Georges Perec (1938-1982) once wrote a book, La disparition, without the letter ‘e’. He was a member of Oulipo group. A quote from the book:

Tout avait l’air normal, mais tout s’affirmait faux. Tout avait l’air normal, d’abord, puis surgissait l’inhumain, l’affolant.Ⅱaurait voulu savoir ou s, articulait l’association qui l’unissait au roman: sur son tapis, assailant atout instant son imagination, l’intution d’un tabou, la vision d’un mal obscure, d’sun quoi vacant, d’un non-dit: la vision, l’avision d’un oubli commandant tout,ou s’abolissait la raison: tout avait l’air normal mais …

Perec would probably have scored high (or rather, low) in the following contest. People are asked to write a perhaps even meaningful text on some subject with as few occurrences of a given ”word” as possible. Our task is to provide the jury with a program that counts these occurrences, in order to obtain a ranking of the competitors. These competitors often write very long texts with nonsense meaning; a sequence of 500,000 consecutive ‘T’s is not unusual. And they never use spaces.

So we want to quickly find out how often a word, i.e., a given string, occurs in a text. More formally: given the alphabet {‘A’,’B’,’C’, …,’Z’} and two finite strings over that alphabet, a word W and a text T ,count the number of occurrences of W in T. All the consecutive characters of W must exactly match consecutive characters of T. Occurrences may overlap.