Problem: If the numbers 1 to 5 are written out in words: one, two, three, four, five, then there are $3+3+5+4+4=19$ letters used in total.

If all the numbers from 1 to 1000 (one thousand) inclusive were written out in words, how many letters would be used?

Note: Do not count spaces or hyphens. For example, 342 (three hundred and forty-two) contains 23 letters and 115 (one hundred and fifteen) contains 20 letters. The use of “and” when writing out numbers is in compliance with British usage.

### Python Solution

This is a relatively straightforward problem, where I don’t see much of a point in trying to optimize it using Cython or C.

import time   start = time.time()   S = [0,3,3,5,4,4,3,5,5,4,3,6,6,8,8,7,7,9,8,8] D = [0,3,6,6,5,5,5,7,6,6] H = 7 T = 8   total = 0 for i in range(1,1000): c = i % 10 # singles digit b = ((i % 100) - c) / 10 # tens digit a = ((i % 1000) - (b * 10) - c) / 100 # hundreds digit   if a != 0: total += S[a] + H # "S[a] hundred if b != 0 or c != 0: total += 3 # "and" if b == 0 or b == 1: total += S[b * 10 + c] else: total += D[b] + S[c]   total += S[1] + T elapsed = time.time() - start   print "%s found in %s seconds" % (total,elapsed)

When executed, we get the following.

21124 found in 0.028256893158 seconds