Thread: last prime factor

Show us your code... I have had this assignment before, and I assume this is homework.

Yes it is homework... i would apreciate any help... this script does almost anything...

Code:

#include<stdio.h>

//declaracion de variables. 
int m, n, I, num;


void LeerDatos()
{
    printf("Ingrese el Primer Numero: ");
    scanf("%d",&m);
    
    printf("Ingrese el Segundo Numero: ");
    scanf("%d",&n);
}

void ejecutar()
{ 
    for (num = m; num <= n; num++) //el contador num  va de m a n
    {  
       for(I = 1; I <= num; I++)//se utiliza la variable I como contador para dividir al "num"
       {
              if (num%I == 0) //si el residuo de num/I es igual a 0,etonces "I" es  un divisor de "num".
              { 
                    printf("\n%hd es divisor de %hd.",I,num);
                    if (I == num)
                    printf("%s","\n"); 
              
              } 
        }
     }   
}


main()
{
LeerDatos();
ejecutar();
getchar();
getchar();

}

Wraithan Show us your code... I have had this assignment before, and I assume this is homework.

I advise you to edit out that last line before you get a verbal punch to the balls (read the guidelines if you're curious why such requests are disapproved of, or lookup the word cheating in the dictionary).
Look around http://www.google.com/search?q=prime+number+algorithm for a prime number algorithm.

It's not whether you are allowed to ask for help or not, and having source to look at is very helpful. But I think a lot of people here would consider that cheating and most people on the board are pretty short with cheaters.
You're sort of on the right track with your current code you're just missing a chunk.

First calculate all primes less than or equal to the number you are given and store them in an array--the first hit for the link I posted above has a whole bunch of algorithms to do that.

Then do something like this:

Code:

for (i = total_number_of_primes_calculated; i != 0; --i)
{
    if ((list_of_primes[i] % the_number_given) == 0)
        printf("The greatest prime which can evenly divide %i is %i", the_number_given, list_of_primes[i]);
}

Don't worry about asking for help, just don't ask for an entire program pre-written to do your homework.

edit:
The above code assumes the array of primes is sorted least to greatest.

Code:

getchar();
getchar();

If there are more characters than you think in the input buffer, that won't work. Use

Code:

int c;  /* must be an int */
while((c = getchar()) != '\n' && c != EOF);
getchar();

See the FAQ: http://faq.cprogramming.com/cgi-bin/...&id=1043284392