Word numbers: Billion approaches (2008)
Word numbers, Part 1: Billion approaches ITA Software recruits computer scientists using puzzles such as the following. If the integers from 1 to 999,999,999 are written as words, sorted alphabetically, and concatenated, what is the 51 billionth letter? In a series of posts, Dylan Thurston and I will solve this problem step by step, introducing concepts such as monoids and differentiation along the way. We will use the programming language Haskell: every post will be a literate program that y