Delete linked list Java

Linked List Insert Methods

Linked List insert methods allow us to insert a Node at a specific place. There are three insert methods based on the position where the new node is inserted.

1. addLast
2. addFirst
3. addAt

1. addLast

As the name suggests, the new node is appended at the last position of the Linked list. The Linked List size is increased by 1. The tail points to the newly added Node. Since we have tail Node, the time complexity is O[1] else it would have been O[n].

2. addFirst

The new node is added at the first position of the Linked list. The Linked List size is increased by 1. The head points at the newly added Node. The time complexity is O[1] as there is no traversal of List is involved.

3. addAt

This method has two arguments the Node to insert and an integer index [say k]. The node is added at the kth position of the Linked list. The linked list size is increased by 1.

In case the element to be added is First or Last then it calls addFirst or addLast respectively.

In this operation, we also use another function getNodeAt which is a private member of Our Linked List class. This function takes an integer index as an argument and if the index is valid [i.e. if index>=0 and index =0 and index = this.size] { throw new Exception["Invalid Index."]; } Node temp = this.head; for [int i = 1; i = this.size] { throw new Exception["Invalid Index."]; } Node temp = this.head; for [int i = 1; i 0] this.tail.next = nn; // dm update if [this.size == 0] { this.head = nn; this.tail = nn; this.size += 1; } else { this.tail = nn; this.size += 1; } } public void addFirst[int item] { // create Node nn = new Node[]; nn.data = item; nn.next = null; // attach nn.next = this.head; // dm update if [this.size == 0] { this.head = nn; this.tail = nn; this.size++; } else { this.head = nn; this.size++; } } public void addAt[int item, int idx] throws Exception { if [idx < 0 || idx > this.size] { throw new Exception["Invalid Index."]; } if [idx == 0] { addFirst[item]; } else if [idx == this.size] { addLast[item]; } else { // create Node nn = new Node[]; nn.data = item; nn.next = null; // attach Node nm1 = getNodeAt[idx - 1]; Node np1 = nm1.next; nm1.next = nn; nn.next = np1; // dm this.size++; } } public int removeFirst[] throws Exception { if [this.size == 0] { throw new Exception["LL is empty."]; } Node temp = this.head; if [this.size == 1] { this.head = null; this.tail = null; this.size = 0; } else { this.head = this.head.next; this.size--; } return temp.data; } public int removeLast[] throws Exception { if [this.size == 0] { throw new Exception["LL is empty."]; } Node temp = this.tail; if [this.size == 1] { this.head = null; this.tail = null; this.size = 0; } else { Node sm2 = getNodeAt[this.size - 2]; sm2.next = null; this.tail = sm2; this.size--; } return temp.data; } public int removeAt[int idx] throws Exception { if [this.size == 0] { throw new Exception["LL is empty."]; } if [idx < 0 || idx >= this.size] { throw new Exception["Invalid Index."]; } if [idx == 0] { return removeFirst[]; } else if [idx == this.size - 1] { return removeLast[]; } else { Node nm1 = getNodeAt[idx - 1]; Node n = nm1.next; Node np1 = n.next; nm1.next = np1; this.size--; return n.data; } } public void display[] { System.out.println["----------------------"]; Node temp = this.head; while [temp != null] { System.out.print[temp.data + " "]; temp = temp.next; } System.out.println["."]; System.out.println["----------------------"]; } public static void main[String[] args] throws Exception { LinkedList1 list = new LinkedList1[]; list.addLast[10]; list.addLast[20]; list.addLast[30]; list.addLast[40]; // this will display the list list.display[]; // 10 should be removed and printed System.out.println[list.removeFirst[]]; list.display[]; // 40 should be removed and printed System.out.println[list.removeLast[]]; list.display[]; // list without 10 and 40 should be printed list.display[]; // 100 should be added at first list.addFirst[100]; list.display[]; // 30 should be removed list.removeAt[2]; list.display[]; // 300 should be added at 2nd index list.addAt[300, 2]; list.display[]; } }

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