euler/problem017.py at master · kju2/euler · GitHub

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"""
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.
"""

NUMBERS = {
    0: "zero",
    1: "one",
    2: "two",
    3: "three",
    4: "four",
    5: "five",
    6: "six",
    7: "seven",
    8: "eight",
    9: "nine",
    10: "ten",
    11: "eleven",
    12: "twelve",
    13: "thirteen",
    14: "fourteen",
    15: "fifteen",
    16: "sixteen",
    17: "seventeen",
    18: "eighteen",
    19: "nineteen",
    20: "twenty",
    30: "thirty",
    40: "forty",
    50: "fifty",
    60: "sixty",
    70: "seventy",
    80: "eighty",
    90: "ninety"
}


def letters_of(number):
    """letters_of returns the amount of letters neccessary to write the given
    number in english words. Tested only from 0 up to the number 9999.

    >>> letters_of(0)
    4
    >>> letters_of(23)
    11
    >>> letters_of(9999)
    36
    """
    if number in NUMBERS:
        return len(NUMBERS[number])

    letters = []

    if number >= 1000:
        letters.append(NUMBERS[number // 1000])
        letters.append("thousand")
        number %= 1000

    if number >= 100:
        letters.append(NUMBERS[number // 100])
        letters.append("hundred")
        number %= 100

        if number != 0:
            letters.append("and")

    if number >= 20:
        letters.append(NUMBERS[(number // 10) * 10])
        number %= 10

    if number > 0:
        letters.append(NUMBERS[number])

    return sum(map(len, letters))


def main():
    """
    >>> main()
    21124
    """
    print(sum(map(letters_of, xrange(1, 1001))))


if __name__ == "__main__":
    import doctest
    doctest.testmod()