ones_tens_hundreds.c

/*

    ones_tens_hundreds.c        by Dragan Milicev


    Find all positive three-digit integers whose digits meet the requirement

    hundreds + tens + ones = hundreds * tens * ones



    You can find all my C programs at Dragan Milicev's pastebin:

    https://pastebin.com/u/dmilicev

*/

#include <stdio.h>

// extract digits from number into array digits[]
// returns the number of extracted digits
int extract_digits_from_number( int number, int digits[20] )
{
    int i, j, number_of_digits = 0, mem;

    while( number != 0 )
    {
        digits[number_of_digits++] = number % 10;   // fill array digits[]
        number = number / 10;
    }

    // reverse first number_of_digits elements of array digits[]
    for ( i=0, j=number_of_digits-1; i<number_of_digits/2; i++, j-- )
    {
        mem = digits[i];
        digits[i] = digits[j];
        digits[j] = mem;
    }

    return( number_of_digits );

} // extract_digits_from_number


int main(void)
{
    int digits[20];         // array to store digits of number
    int i, counter=0;

    for ( i=100; i<1000; i++)
    {
        extract_digits_from_number( i, digits );

        if ( digits[0]+digits[1]+digits[2] == digits[0]*digits[1]*digits[2] )
        {
            counter++;
            printf("\n %4d. \t %5d \n", counter, i );
        }
    }

    printf("\n\n From 100 to 999, there are %d such numbers. \n\n", counter );


    return 0;

} // main()