problem-017.py

"""
Problem 17

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?
"""

import math


def num_of_letters(n: int) -> int:
    """
    Parameters
        n (int): upper range of numbers to add letters [1, n]
    Returns
        num_letters (int): number of letters in [1, n]
    """

    num_letters = 0
    lett = {
        "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,
        "20": 6,
        "30": 6,
        "40": 5,
        "50": 5,
        "60": 5,
        "70": 7,
        "80": 6,
        "90": 6,
        "100": 7,
        "1000": 8,
    }

    for i in range(1, n + 1):
        current_num = i
        if current_num == 1000:
            num_letters += lett["1"] + lett["1000"]
            current_num -= 1000
        if math.floor(current_num / 100.0) > 0:
            num_letters += lett["100"]
            num_letters += lett[str(math.floor(i / 100.0))]
            current_num -= math.floor(current_num / 100.0) * 100
        if i > 100 and i % 100 != 0:
            num_letters += 3  # for 'and'
        if math.floor(current_num / 90.0) > 0:
            num_letters += lett["90"]
            current_num -= 90
        if math.floor(current_num / 80.0) > 0:
            num_letters += lett["80"]
            current_num -= 80
        if math.floor(current_num / 70.0) > 0:
            num_letters += lett["70"]
            current_num -= 70
        if math.floor(current_num / 60.0) > 0:
            num_letters += lett["60"]
            current_num -= 60
        if math.floor(current_num / 50.0) > 0:
            num_letters += lett["50"]
            current_num -= 50
        if math.floor(current_num / 40.0) > 0:
            num_letters += lett["40"]
            current_num -= 40
        if math.floor(current_num / 30.0) > 0:
            num_letters += lett["30"]
            current_num -= 30
        if math.floor(current_num / 20.0) > 0:
            num_letters += lett["20"]
            current_num -= 20
        if str(current_num) in lett:
            num_letters += lett[str(current_num)]
    return num_letters


print("Number of letters in 1 to 1000: " + str(num_of_letters(1000)))