Question

Given the following linked list structure called node:

struct node {

int val;

struct node * ptrNext;

};

Assume we have a single list created from this structure with a head pointer called ptrFirst which is declared in the global scope.

a. Write a complete C function called CountEven to count all the even values in this singly linked list of arbitrary number of nodes using an iterative (non-recursive) approach. The function takes as parameter the pointer to the starting node in the list, and returns an integer indicating the number of nodes with even values found in the list.

b. Write a complete C function called CountEvenRecursive to count all the even values in this singly linked list of arbitrary number of nodes using a recursive approach. The function takes as parameter the pointer to the starting node in the list, and returns an integer indicating the number of nodes with even values found in the list.

Answer 1

int CountEven(struct node* first){
    int s = 0, n;
    while(first!=NULL){
        n = first->val;
        if(n%2==0){
            s = s + n;
        }
        first = first->next;
    }
    return s;
}


int CountEvenRecursive(struct node* first){
    if(first!=NULL){
        if((first->val)%2==0){
            return (first->val) + CountEvenRecursive(first->next); 
        }
        else{
            return CountEvenRecursive(first->next);
        }
    }
    else{
        return 0;
    }
}