Reversing_Linked_List.cpp

#include<iostream>
using namespace std;

class node{
public:
    int data;
    node* next;

    node(int val)
    {
        data=val;
        next=NULL;
    }
};

void insertAtHead(node* &head, int val)
{
    node* n = new node(val);
    n->next=head;
    head=n;
}

void insertAtTail(node* &head, int val)   //Putting the value using call by refence (head) value because here we are modifying our link list
{
    node* n = new node(val);
    if(head==NULL)
    {
        head=n;
        return;
    }

    node* temp=head;
    while(temp->next!=NULL)
    {
        temp=temp->next;
    }
    temp->next=n;
}

void display(node* head)  //Calling the function by value
{
    node* temp=head;
    while(temp!=NULL)
    {
        cout<<temp->data<<"->";
        temp=temp->next;
    }
    cout<<"NULL"<<endl;
}

node* reverse(node* &head)
{
    node* prevptr=NULL;
    node* currptr=head;
    node* nextptr;

    while(currptr!=NULL)
    {
        nextptr=currptr->next;
        currptr->next=prevptr;

        prevptr=currptr;
        currptr=nextptr;
    }

    return prevptr;
}

int main()
{
    node* head=NULL;
    insertAtTail(head,1);
    insertAtTail(head,2);
    insertAtTail(head,3);
    insertAtTail(head,4);

    display(head);
    node* newhead=reverse(head);
    display(newhead);
    return 0;
}