p017.py

# Steve Beal
# Project Euler problem 17 solution
# 2/12/14

# 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 are 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.

under_20_len = {1:3, 2:3, 3:5, 4:4, 5:4, 6:3, 7:5, 8:5, 9:4, 10:3, 11:6,
                12:6, 13:8, 14:8, 15:7, 16:7, 17:9, 18:8, 19:8}

tens_place_len = {2:6, 3:6, 4:5, 5:5, 6:5, 7:7, 8:6, 9:6}

len_hundred = 7
len_thousand = 8
len_and = 3

def letters_in_number_words(start, end):

    total_letters = 0
    for i in range(start, end+1):
        if i > 0 and i <= 9999:
            if i >= 1000:
                total_letters += len_thousand + under_20_len[i//1000]
                i %= 1000
            if i >= 100:
                total_letters += len_hundred + under_20_len[i//100]
                if i % 100 != 0:
                    total_letters += len_and
                i %= 100
            if i >= 20:
                total_letters += tens_place_len[i//10]
                i %= 10
            if i in under_20_len:
                total_letters += under_20_len[i]
        else:
            raise ValueError("Value must be between 0 and 10,000, exclusive")
            break
    return total_letters

print(letters_in_number_words(1, 1000))