Question

Please fill in this code to reverse a linked list: (written in C/C++)

#include  
#include  
#include 

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

IDEONE Link: https://ideone.com/xyoCMR

Raw Code:

Used stack to reverse the linked list.

#include <iostream>
using namespace std;

#include<bits/stdc++.h>

using namespace std;

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

/* Function to reverse the linked list */
static void reverse(struct Node** head_ref)
{
// your code here
struct Node *head = *head_ref;
stack<int> s;
struct Node*temp = head;
while(temp!=NULL){
s.push(temp->data);
temp = temp->next;
}
temp = head;
while(temp!=NULL){
temp->data = s.top();
s.pop();
temp = temp->next;
}
//return head;
*head_ref = head;
}

/* Function to push a node */
void push(struct Node** head_ref, int new_data)
{
// your code here
Node *t = new Node();
t->data = new_data;
t->next = *head_ref;
*head_ref = t;
}

/* 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);
}