In your solution, you have to deal with an annoying corner case : if the node is to be inserted in front of the list, then you cannot just apply a setNext(newNode) to the previous node, since there is no previous node. Instead, you have to deal with the attribute head just for this specific case. You can greatly simplify things if you introduce a "root" node. This root node will always exist in the LinkedList (So, an empty list is composed of only one Node : the root). Using this convention, I can implement your method with 9 lines of code, containing only one loop. I will post this solution if you want to (I don't know if it is ok to give his own solution on this site, and maybe you'd like to try on your own before I post my implementation). to answer the question 2, I think implementing such a method is not an easy task, because it is not natural for our human brain to reason about a recursive data type. And if you introduce corner cases as you did, you quickly become overwhelmed by what you have to keep in mind in order to design your algorithm. Here is what I did in order to implement your method :
After some iterations, I realized it was almost working, except for the corner case (insertions in front of the list). I introduced the root Node, and my algorithm worked. EditHere is my implementation : public class LinkedList<T> { private static class Node<T> { private T value; private Node next; public Node(T value) { this.value = value; } } private Node root = new Node(null); public void add(int i, T v) { Node n = root; while(i>0) { if (n.next == null) { throw new ArrayIndexOutOfBoundsException(); } n = n.next; i--; } Node newNode = new Node(v); newNode.next = n.next; n.next = newNode; } }
The linked list is one of the most important data structures to learn while preparing for interviews. Having a good grasp of Linked Lists can be a huge plus point in a coding interview. In this article, we are going to learn how to use the LinkedList add() method in Java. The add() method adds an element to the list. There are two variations of the LinkedList add() method. Let us have a glance at the approaches of both of them. Approach and Algorithmadd(Object X) methodIn this method, we pass an object X as a parameter to this function. As a result, this function appends the object element passed to the end of the list. Syntax: boolean add(Object X) Note: It returns true only if the action of append is performed. Code Implementation
import java.io.*; import java.util.LinkedList; public class LinkedListDemo { public static void main(String args[]) { LinkedList list = new LinkedList(); list.add("Coding"); list.add("is"); list.add("Fun"); list.add("10"); list.add("20"); System.out.println("The list is:" + list); list.add("Computer"); System.out.println("The new List is:" + list); } } OutputThe list is:[Coding, is, Fun, 10, 20] Time Complexity: O(1), as the new object is being added to the end of the list, which takes constant time. Approach and Algorithmadd(int index,Collection X) methodIn this method, we pass a Object X and an index as parameters to this function. As a result, this function appends the element passed to the specified index that is passed as a parameter. Syntax: void add(int index,Object X) Note: No value is returned by this method. Code Implementation
import java.io.*; import java.util.LinkedList; public class LinkedListDemo { public static void main(String args[]) { LinkedList list = new LinkedList(); list.add("Coding"); list.add("is"); list.add("Fun"); list.add("10"); list.add("20"); System.out.println("The list is:" + list); //Here we are talking about this add method which //takes index and a object as parameter list.add(2, "Super"); System.out.println("The new List is:" + list); } } OutputThe list is:[Coding, is, Fun, 10, 20] Time Complexity: O(n), as we have to traverse the given index to add the element. So, in this article, we have tried to explain how to use LinkedList add() method in Java. Java Collections is an important topic when it comes to coding interviews. If you want to solve more questions on Linked List, which are curated by our expert mentors at PrepBytes, you can follow this link Linked List.
In this article, we are going to cover in-depth how to implement Linked List in Java. First, we will start with a little bit of theory about what a LinkedList data structure is. Then, we are going to dig deep to see how to create a linked list implementation in Java using practical examples. A LinkedList, also called singly linked list, is a dynamic data structure that describes a collection of data where all elements are linked together. Basically, each element of the list is linked to the next one, hence the name. Confused? Let me explain: Like a chain, each element is linked to its next neighbor. Since a linked list is not an infinite loop, it must end somewhere. So, just after the last element, we find the null reference to indicate the end of the list. Typically, each element of a linked list is called a node. Each node holds two items:
The first node that defines the entry point into the list is called a head. Please bear in mind that there are two types of linked lists: single and double linked lists. However, in this tutorial we will be concentrating on how to implement singly linked lists. Our article on how to implement a doubly linked list in Java does a great job in covering this topic. As we have mentioned earlier, a singly LinkedList is a dynamic list where its elements are chained together and organized linearly. Linked lists and arrays are similar since they both can be used to store linear data. However, unlike arrays, linked list elements are not stored in sequential memory locations, they are all linked in a linear way. Now, that we know what a linked list data structure is, let’s see how to implement it in Java. Understanding how to implement a LinkedList from scratch will help us understand more complex data structures. So, let’s see how we can accomplish this in Java. In short, to implement a linked list, we need to define its core components: the node and the head. In Java, a linked list can be represented as a simple class that contains another separate Node class. To define the head, our class should have a reference of Node type. Now, let’s put all the pieces together and see how a linked list can be implemented in Java: public class SinglyLinkedList<T> implements Iterable<T>{ private Node<T> head; public SinglyLinkedList() { this.head = null; } private static class Node<T>{ private T data; private Node<T> next; public Node(T data, Node<T> next){ this.data = data; this.next = next; } } }As we can see, the Node class contains the data and a reference to the next node. We call our implementation SinglyLinkedList because each node has only one reference to point to the next one. Next, let’s see how to implement some basic operations. Basic Operations
To reverse a singly linked list in java, we have to change the current node’s next link to point to its previous element. To do so, we need 3 references:
(n-1) –> (n) –> (n+1) –> … Since each item does not have a reference link to the previous node, then we must store the previous element somewhere. We can achieve this using the following simple statement: current.next = previous;We need a third reference to store the next node before changing the references to keep track on the next elements. The logic of reversing a linked list in Java can be described as follow:
Cloning in java, refers to the process of creating an exact copy from an original object. The basic idea of cloning a linked list is to iterate through it to create a new copy that holds the same elements. Let’s see together how to clone a linked list in Java:
The Collection API provides a convenient way to implement a linked list in Java. It comes with a ready-to-use class named LinkedList. So, let’s see together how to use LinkedList and what feature brings in: public static void main(String[] args) { LinkedList languages = new LinkedList<>(); languages.add("Java"); languages.addFirst("PHP"); languages.addLast("Python"); languages.add("C++"); languages.add("JavaScript"); languages.add("C#"); languages.add("Kotlin"); System.out.println("First Language: " + languages.getFirst()); System.out.println("Last Language: " + languages.getLast()); languages.removeFirst(); languages.removeLast(); languages.forEach(System.out::println); } ### Output: First Language: PHP Last Language: Kotlin Java Python C++ JavaScript C#As we can see, LinkedList offers a set of methods for adding, retrieving, and removing elements from a linked list. Please feel free to check our tutorial on Java priority queue. ConclusionThat’s all folks! we have explained how to implement linked list in Java and explored some of the most common operations. We hope this article will help you in getting started with LinkedList in Java programming. Thank you for reading. Please drop me a comment on what you think about this topic or if you like to add something. |