Question

Please fill in the code to reverse a linked list. IN C++

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

using namespace std;

/* Link list node */
struct Node { 
        int data; 
        // your code here
}; 

/* Function to reverse the linked list */
static void reverse(struct Node** head_ref) 
{ 
        // your code here 
} 

/* Function to push a node */
void push(struct Node** head_ref, int new_data) 
{ 
        // your code here 
} 

/* Function to print linked list */
void printList(struct Node* head) 
{ 
        struct Node* temp = head; 
        while (temp != NULL) { 
                cout << temp->data << " "; 
                temp = temp->next; 
        } 
} 

/* Driver program to test above function*/
int main() 
{ 
        /* Start with the empty list */
        struct Node* head = NULL; 

        push(&head, 10); 
        push(&head, 20); 
        push(&head, 15); 
        push(&head, 85); 

        cout << "Forward list\n"; 
        printList(head); 
        reverse(&head); 
        cout << "\nReversed list \n"; 
        printList(head); 
} 

Answer 1

Here is the completed code for this problem. Comments are included, go through it, learn how things work and let me know if you have any doubts or if you need anything to change. If you are satisfied with the solution, please rate the answer. If not, PLEASE let me know before you rate, I’ll help you fix whatever issues. Thanks

#include <stdio.h>

#include <stdlib.h>

#include <iostream>

using namespace std;

/* Link list node */

struct Node {

        int data;

        Node* next;

};

/* Function to reverse the linked list */

static void reverse(struct Node** head_ref)

{

              //taking a reference to head node

    Node* curr=*head_ref;

    //initializing two Node* variables to NULL

    Node* prev=NULL;

    Node* next=NULL;

    //looping until curr is NULL

    while(curr!=NULL){

            //storing next of curr in next

              next=curr->next;

              //setting prev as new next node of prev

              curr->next=prev;

              //assigning curr to prev

              prev=curr;

              //and setting next as new curr

              curr=next;

              }

              //finally, setting prev as new head node

              *head_ref=prev;

}

/* Function to push a node */

void push(struct Node** head_ref, int new_data)

{

              //creating new node, setting data

    Node* node=new Node();

    node->data=new_data;

    //if head is null, adding as head node

    if(*head_ref==NULL){

              *head_ref=node;

              }else{

                             //taking reference to head

                             Node* current=*head_ref;

                             //looping until current is the last node

                             while(current->next!=NULL){

                                           current=current->next;

                             }

                             //adding node as the next of current

                             current->next=node;

              }

}

/* Function to print linked list */

void printList(struct Node* head)

{

        struct Node* temp = head;

        while (temp != NULL) {

                cout << temp->data << " ";

                temp = temp->next;

        }

}

/* Driver program to test above function*/

int main()

{

        /* Start with the empty list */

        struct Node* head = NULL;

        push(&head, 10);

        push(&head, 20);

        push(&head, 15);

        push(&head, 85);

        cout << "Forward list\n";

        printList(head);

        reverse(&head);

        cout << "\nReversed list \n";

        printList(head);

}

/*OUTPUT*/

Forward list

10 20 15 85

Reversed list

85 15 20 10