Converting an iterative function to recursive

Question

I know people usually ask this question the other way round, but I have the following problem: I have this iterative function which counts all the nodes in a circular doubly

Answer 1

How about this :

int count(node *start){  
   if(!start) return 0;  
   int countValue = 0; 
   return count(start,start,&countValue);
}


int count(node *start, node *next, int *count){  
    if(start == next)//circular list so this is your base
       return *count;
    if(next->next->roll_no) == 20){  
         *count++;
    }  
    return count(start,next->next,count);  
}

It is not custom for recursive functions to modify input params though.
Nor to use use global variable.
This is the first approach I could come up