nth node from the end

 There are 2 approaches. 1. LENGTH OF LL 2.TWO POINTER APPROACH

Note: node*& : reference to a pointer/ pointer reference

node* : simple pointer to iterate over a ll

node** : to point to the head of ll- for head manipulation

 

Node is a data type.

1.USING LENGTH OF THE LL

#include <iostream>

#include <bits/stdc++.h>

using namespace std;

//nth node from the end

class Node{

    public:

    int data;

   struct Node* next;

    };

    

//function to get the nth node from the last of Linkedlist;

void printnthfromlast(struct Node*head, int n){

    int len=0,i;

    struct Node* temp=head; //temp node points to head

    while(temp!=NULL){

        temp= temp->next;

        len++;

        

    }

  if(len<n)

  return;

  temp= head;

  for (i=1; i<len-n+1; i++)

  temp= temp->next;

  cout<<temp->data;

  return;

    

}

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

   struct Node* new_node= new Node();

   new_node->data= new_data;

   new_node->next= (*head_ref);

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

}

int main() {

  struct Node* head= NULL; //create an empty linkedlist

  push(&head, 20);

  push(&head, 4);

  push(&head, 15);

  push(&head, 35);

  printnthfromlast(head, 4);

return 0;

}

2.TWO POINTER APPROACH

#include <iostream>

using namespace std;

#include <bits/stdc++.h>

//2POINTER APPROACH

struct Node{

    int data;

     struct Node* next;

    };

    

//function to get nth node from the last

void printnthfromlast(struct Node* head, int n)

{

   struct Node *main_ptr= head;

   struct Node *ref_ptr= head;

    int count=0;

   if(head!=NULL)

   {

       while(count<n)

       {  if(ref_ptr==NULL)

         {

           printf("%d is greater than the no of" "nodes in list", n );

           return;

         } //if ends

            ref_ptr = ref_ptr->next;

            count++;

       } //while loop ends

       

   

    

    if(ref_ptr==NULL)

    {

       head= head->next;

       if (head!= NULL) 

       

           printf("Node no. %d from last is %d", n, main_ptr->data);

           

    }//if++ ends   

       else 

       {

           while (ref_ptr!= NULL)

           {

               main_ptr= main_ptr->next;

               ref_ptr= ref_ptr->next;

           }//while ends

           printf("Node no.%d from last is %d", n, main_ptr->data);

       }//else ends

    }

}

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

    { struct Node* new_node= new Node();

      new_node->data= new_data;

      new_node->next= (*head_ref);

      (*head_ref)= new_node;  

        

    }

    

    

int main() {

struct Node* head= NULL;

push(&head, 20);

push(&head, 4);

push(&head, 15);

push(&head, 35);

printnthfromlast(head, 4);

return 0;

}