A solution to the number-to-words problem presented at ITA:

  http://www.itasoftware.com/careers/puzzle_archive.html

and rekindled by Nathan Wong:

  http://nathan.ca/2011/12/ita-word-numbers/


All the integers between 1, and 999,999,999 are spelled out as
words and then sorted alphabetically into a list.  Letters are
counted from the start of the list and the integer that completes
just as 51 billion letters have been scanned, is printed out.

A typical run on a 1.6Ghz machine is very quick:

  $ time ./solve
  Final Integer: 676746575
  Written as: sixhundredseventysixmillionsevenhundredfortysixthousandfivehundredseventyfive
  Integer Sum: 413540008163475743
  Character Count: 51000000000
  Number of integers: 723302492
  
  real    0m0.004s
  user    0m0.003s
  sys     0m0.001s

A program (gen.c) is also included that was used to generate the "data.h"
source file which contains the tables used to iterate through the sorted
number-words.