Thread: Recursive functions

Hello guys,i'm new to c programming and programming in general.

I have a question about recursive functions .

My questions are(so far)(with reference to tutorialspoint.com about:recursion)

1.Why this isn't an infinte loop?
2.What is the original value of i when the programme starts?
3.Is there any problem if i write the main() function 1st and not the factorial() function?

This is the code tutorialspoint.com provides:

Code:

include<stdio.h>
int factorial(unsigned int i) 
{

   if(i <= 1) 
{
      return 1;
   }
   return i * factorial(i - 1);
}

int  main() 
{
   int i = 15;
   printf("Factorial of %d is %d\n", i, factorial(i));
   return 0; 
}

Output:Factorial of 15 is 2004310016

Also i would like some help on my programme about recursive functions:

This is the excercise:

Write a RECURSIVE functions that checks if in an array that consists of ten [10] there is on quartet of integer numbers A,B,C,D so that A+D=B+C

For example, the array 5 10 20 21 31 4 3 9 contains the integers 10 20 21 31 that meet the requirements

Your recursive function must print a message to point whether the array input contains a suitable quartet of numbers, the pointer of the 1st number of the quartet, and the 4 numbers.Your recursive function must return the pointer of the 1st number of the quartet.In case of failure, a proper message must be printed and your function must return -1;

YOU ARE NOT ALLOWED TO USE AND LOOPS OR GLOBAL/STATIC VARIABLES.

______

This is my code so far(neither built or debugged as i know i have many mistakes that i can't spot )

Code:

#include <stdio.h>#include <stdlib.h>


int quadruple(int i)
{
    int j=0,a[10];
    int *ptr;
    if (j>7)
    {
        return -1;
        printf("There are no numbers so that A+D=B+C is true");
    }
    else if ((a[j+1]+a[j+4])=(a[j+2]+a[j+3]))
    {
        ptr=&a[j+1];
        printf("There is a suitable quartet of numbers");
        printf("The numbers are:%d %d %d %d", a[j+1],a[j+2],a[j+3],a[j+4])
        printf("The position of the 1st digit is :%d", ptr);
        return ptr;
        j++;
    }
    return quadruple(i, a[10]);


}




int main ()
{
    int i=10,a[10];
    quadruple(i, a[10]);
    return 0;
}

Pretty confused here guys.


Sorry for any grammar,vocab.,syntax mistakes.English is not my native lang.

Just looking at the first example:

a) It's not an infinite loop because you have what is called (most commonly these days) a base case that stops the recursive calls.
b) The answer is not correct (presumably because of integer overflow)

Hmmm ,thanks Hodor!

Originally Posted by George Ioannou

Hmmm ,thanks Hodor!

Ok, great. So you understand now. The thread can be closed?