Question

Write an iterative and recursive version of a function to print out a linked list from head to tail and then do the same for printing a linked list from tail to head. Assume a singly linked list in all cases and access only to a head pointer at the time of the function call. struct node; typedef struct node Node; struct node int data; Node next;

C programming

Answer 1

#include<stdio.h>

#include<stdlib.h>

/* Link list node */

struct Node

{

int data;

struct Node* next;

};

/* Function to reverse the linked list */

void tailToHead(struct Node* head)

{

// Base case

if (!head)

return;

// print the list after head node

tailToHead(head->next);

// After everything else is printed, print head

printf("%d ", head->data);

}

void headToTail(struct Node* head)

{

// Base case

if (!head)

return;

// After everything else is printed, print head

printf("%d ", head->data);

// print the list after head node

headToTail(head->next);

}

void iheadToTail(struct Node* head)

{

while (head!= NULL)

{

// print current data

printf("%d ", head->data);

// increase pointer

head=head->next;

}

}

/*UTILITY FUNCTIONS*/

/* Push a node to linked list. Note that this function

changes the head */

void push(struct Node** head_ref, char 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 off the new node */

new_node->next = (*head_ref);

/* move the head to pochar to the new node */

(*head_ref) = new_node;

}

/* Drier program to test above function*/

int main()

{

// Let us create linked list 10->20->30->40

struct Node* head = NULL;

push(&head, 40);

push(&head, 30);

push(&head, 20);

push(&head, 10);

printf("\nrecursive Head to tail \n");

headToTail(head);

printf("\n iterative Head to tail \n");

iheadToTail(head);

printf(" \n recursive Tail to Head \n");

tailToHead(head);

return 0;

}

Output:-

recursive Head to tail 
10 20 30 40 
 iterative Head to tail 
10 20 30 40  
 recursive Tail to Head 
40 30 20 10