Thread: For loop issues

I'm about as new as they come to programming. Taking a class on it for the first time this semester. I'm writing a program that takes an integer (n) as the input and outputs every integer from 1 to n, their factorials, and the factorials of (n-1).

It should look something like this:

n	n!	(n-1)!
1	1	1
2	2	1
3	6	2
4	24	6

The problem is that instead of outputting the subsequent integers, I'm getting the final line repeated n times.

Also aware this might not be the most efficient way to do this. That's a secondary concern right now.

Code:

 #include <stdio.h>

int main(void)
{
    int i, j; //Variables for output lines 1 to n-1
    int n, start, factor, fin; //n! variables
    int startm, factorm, finm; //(n-1)! variables

    printf("Please enter the number of factorials you wish to output: ");
    scanf_s("%i", &n);
    printf("  n   n!   (n-1)!\n-------------------\n");
        
    
    //start of output lines 1 to n-1 loop
    for (i = 1; i <= n; i++) {


        //start of n! loop
        for (start = 1; start <= n; start++) {
            fin = 1;


            for (factor = 1; factor <= n; factor++) {
                fin = fin*factor;
            }

        }
        //start of (n-1)! loop
        for (startm = 1; startm <= n; startm++) {
            finm = 1;


            for (factorm = 1; factorm < n; factorm++) {
                finm = finm*factorm;
            }

        }
        
        
        printf("%i %i %i\n", n, fin, finm);
    }
    
    getch();
    return(0);
}

Thanks so much!

No problem. Actually, my "obvious" way to make it more efficient didn't go far enough. Imagine if you were only printing out i!. Then all you would need is the outer loop. But (i-1)! is just the last iteration's i!, so all you need is the outer loop calculating the current i! (by multiplying the last one by i) and also a variable to remember the previous answer. Only one loop is needed.

I turned it in today. Managed to be one of the few kids whos programs ran properly without a bunch of extra work I didn't use it but your most efficient way is more efficient than my teacher's. Thanks again btw

Good job!

Code:

    int i, f = 1;
    for (i = 1; i <= n; f *= i++)
        printf("%3d %8d %8d\n", i, f * i, f);