In This Post, We will learn How to find Nth node from the end of a Singly Linked List in Java?
Complete Source code :
Program Logic is Very Simple:
- We defined two Node references/Pointers(mainPointer & refPointer) and both will be initialized to the head node.
- First iterate refPointer to N nodes.
- Then iterate both node pointers (mainPointer & refPointer) one step at a time, till refPointer node is null.
- Once Setp-3 is completed, the mainPointer represents the Nth node from the end node
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package com.kkjavatutorials.util; /** * How to find Nth node from the end of a Singly Linked List in Java ? * @author KK JavaTutorials */ public class LinkedList<T> { private Node<T> head; //This internal class represents Node in Linked List private static class Node<T>{ private T data; private Node<T> next; public Node(T data) { super(); this.data = data; this.next = null; } } /** * This method insert a Node in Linked List * @param data has to insert in the List */ public void insert(T data) { Node<T> newNode = new Node<T>(data); if(head == null) { head = newNode; }else { Node<T> currentNode = head; while (currentNode.next != null) { currentNode = currentNode.next; } currentNode.next = newNode; } } /** * Method which traverse Linked List and display all data. */ public void displayLinkedList() { Node<T> currentNode = head; while(currentNode!= null) { System.out.print(currentNode.data+" "); currentNode = currentNode.next; } } /** * This Method returns Nth node from the end of a Singly Linked List in Java * @param n node number from end of a List * @return Nth Node from the end of a List */ public T findNthNodeFromEnd(int n) { if(head == null) { return null; } if(n<=0) { throw new IllegalArgumentException("Invalid Value of n ="+n); } Node<T> mainPointer = head; Node<T> refPointer = head; int count = 0; while(count < n) { if(refPointer == null) { throw new IllegalArgumentException("Valus of n ="+n+" is greater than number of nodes in the list!!"); } refPointer = refPointer.next; count++; } while(refPointer !=null) { refPointer = refPointer.next; mainPointer = mainPointer.next; } T result = mainPointer.data; return result; } public static void main(String[] args) { LinkedList<Integer> linkedList = new LinkedList<>(); linkedList.insert(10); linkedList.insert(20); linkedList.insert(30); linkedList.insert(40); linkedList.insert(50); linkedList.insert(60); System.out.println("Linked List is:"); linkedList.displayLinkedList(); System.out.println(); int NthNodeFromEnd = 3; System.out.println("3rd Node from end of the List is :"+linkedList.findNthNodeFromEnd(NthNodeFromEnd)); } } |
Output of this Program:
Linked List is:
10 20 30 40 50 60
3rd Node from end of the List is :40
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