C Program To Check If Two Linked Lists Are Identical

// An iterative C program to check if 
// two linked lists are
// identical or not
#include<stdio.h>
#include<stdlib.h>
#include<stdbool.h>

// Structure for a linked list node 
struct Node
{
    int data;
    struct Node *next;
};

/* Returns true if linked lists a and b 
   are identical, otherwise false */
bool areIdentical(struct Node *a, 
                  struct Node *b)
{
    while (a != NULL && b != NULL)
    {
        if (a->data != b->data)
            return false;

        /* If we reach here, then a and b 
           are not NULL and their data is 
           same, so move to next nodes in 
           both lists */
        a = a->next;
        b = b->next;
    }

    // If linked lists are identical, then 
    // 'a' and 'b' must be NULL at this point.
    return (a == NULL && b == NULL);
}

/* UTILITY FUNCTIONS TO TEST fun1() 
   and fun2() */
/* Given a reference (pointer to pointer) 
   to the head of a list and an int, push 
   a new node on the front of the list. */
void push(struct Node** head_ref, 
          int new_data)
{
    // Allocate node 
    struct Node* new_node =
           (struct Node*) malloc(sizeof(struct Node));

    // Put in the data  
    new_node->data = new_data;

    // Link the old list of the new node 
    new_node->next = (*head_ref);

    // Move the head to point to the 
    // new node 
    (*head_ref) = new_node;
}

// Driver code
int main()
{
    /* The constructed linked lists are :
       a: 3->2->1
       b: 3->2->1 */
    struct Node *a = NULL;
    struct Node *b = NULL;
    push(&a, 1);
    push(&a, 2);
    push(&a, 3);
    push(&b, 1);
    push(&b, 2);
    push(&b, 3);

    areIdentical(a, b)? printf("Identical"):
                        printf("Not identical");
    return 0;
}

// A recursive C function to check if 
// two linked lists are identical or not
bool areIdentical(struct Node *a, 
                  struct Node *b)
{
    // If both lists are empty
    if (a == NULL && b == NULL)
       return true;

    // If both lists are not empty, then 
    // data of current nodes must match, 
    // and same should be recursively true 
    // for rest of the nodes.
    if (a != NULL && b != NULL)
       return (a->data == b->data) &&
              areIdentical(a->next, b->next);

    // If we reach here, then one of the lists
    // is empty and other is not
    return false;
}