Project Euler Problem 17

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?

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.

 

#include <stdio.h>



int numLetters1_19[] =

{

    sizeof("one") - 1,

    sizeof("two") - 1,

    sizeof("three") - 1,

    sizeof("four") - 1,

    sizeof("five") - 1,

    sizeof("six") - 1,

    sizeof("seven") - 1,

    sizeof("eight") - 1,

    sizeof("nine") - 1,

    sizeof("ten") - 1,

    sizeof("eleven") - 1,

    sizeof("twelve") - 1,

    sizeof("thirteen") - 1,

    sizeof("fourteen") - 1,

    sizeof("fifteen") - 1,

    sizeof("sixteen") - 1,

    sizeof("seventeen") - 1,

    sizeof("eighteen") - 1,

    sizeof("nineteen") - 1,

};



int numLetters2Tens[] =

{

    sizeof("twenty") - 1,

    sizeof("thirty") - 1,

    sizeof("forty") - 1,

    sizeof("fifty") - 1,

    sizeof("sixty") - 1,

    sizeof("seventy") - 1,

    sizeof("eighty") - 1,

    sizeof("ninety") - 1,

};



#define GET_NUM_LETTERS_1_19(N) numLetters1_19[N - 1]

#define GET_NUM_LETTERS_2Tens(N) numLetters2Tens[N - 2]



int numLettersHundred = sizeof("hundred") - 1;

int numLettersAnd = sizeof("and") - 1;

int numLettersThound = sizeof("thousand") - 1;



int countLettersLessThan1000(int num)

{

    int numLetters = 0;



    int nThousand = num / 1000;

    if (nThousand > 0)

    {

        numLetters += GET_NUM_LETTERS_1_19(nThousand);

        numLetters += numLettersThound;

    }



    num = num % 1000;



    int nHundred = num / 100;

    bool hasHundred = false;

    if (nHundred > 0)

    {

        numLetters += GET_NUM_LETTERS_1_19(nHundred);

        numLetters += numLettersHundred;

        hasHundred = true;

    }



    num = num % 100;



    if (num > 0)

    {

        if (hasHundred)

        {

            numLetters += numLettersAnd;

        }



        if (num <= 19)

        {

            numLetters += GET_NUM_LETTERS_1_19(num);

        }

        else

        {

            int nTens = num / 10;

            numLetters += GET_NUM_LETTERS_2Tens(nTens);



            num = num % 10;



            if (num > 0)

            {

                numLetters += GET_NUM_LETTERS_1_19(num);

            }

        }

    }



    return numLetters;

}



int main(int argc, char* argv[])

{

    int totalNumLetters = 0;



    for (int i = 1; i <= 1000; ++i)

    {

        totalNumLetters += countLettersLessThan1000(i);

    }



    printf("%d\n", totalNumLetters);



    return 0;

}