Merge pull request #28 from suryansh-sinha/main

Implemented Singly Linked List in Java.

Author: Jayanti2919

.DS_Store

@@ -0,0 +1,138 @@
+public class LinkedList {
+
+    private Node head;  // Reference variable pointing to nodes.
+    private Node tail;  // Reference variable pointing to nodes.
+    private int size;   // Number of elements in the linked list.
+    public LinkedList(){
+        this.size=0;
+    }
+
+    private class Node {
+
+        private int value;
+        private Node next;
+
+        public Node(int value) {
+            this.value = value;
+        }
+
+        public Node(int value, Node next){
+            this.value = value;
+            this.next = next;
+        }
+    }
+
+    // Inserting a new node at the starting of the list.
+    public void insertFirst(int val){
+        Node node = new Node(val);
+        node.next = head;   // Assigning the newly created node to point to the previous head.
+        head = node;    // Changing the head to the current node.
+
+        if (tail == null)
+            tail = head;    // If this is the only node in the list, then tail also points to this address.
+
+        size += 1;  // Increasing the size of the list coz new element added.
+    }
+
+    // Inserting a new node at the end of the list.
+    public void insertLast(int val){
+        if (tail == null)
+            insertFirst(val);
+        else {
+            Node node = new Node(val);
+            tail.next = node;
+            tail = node;
+            size += 1;
+        }
+    }
+
+    // Inserting a new node at any given list
+    public void insert(int val, int index){
+        if (index == 0) {
+            insertFirst(val);
+            return;
+        }
+
+        if(index == size){
+            insertLast(val);
+            return;
+        }
+
+        Node temp = head;
+        for (int i = 1; i < index; i++) {
+            temp = temp.next;   // Reaching before the node where we want to insert our value.
+        }
+        Node node = new Node(val, temp.next);   // Pointing the new node to the next value of the temporary node.
+        temp.next = node;
+        size++;
+        }
+
+    // Delete node at the first index.
+    public int deleteFirst(){
+        int val = head.value;
+        head = head.next;
+        if(head==null){
+            tail = null;
+        }
+        size -= 1;
+        return val;
+    }
+
+    // Delete node at the last index.
+    public int deleteLast(){
+        if(size <= 1){
+            return deleteFirst();
+        }
+
+        Node secondLast = get(size - 2);
+        int value = tail.value;
+        tail = secondLast;
+        tail.next = null;
+        size -= 1;
+        return value;
+    }
+
+    // To delete a node at given index.
+    public int delete(int index){
+        if (index == 0)
+            return deleteFirst();
+        if (index == size-1)
+            return deleteLast();
+        Node prev = get(index - 1);
+        Node deleted = prev.next;
+        int val = deleted.value;
+        prev.next = deleted.next;
+        size -= 1;
+        return val;
+    }
+
+    // To return a node that has a particular value.
+    public Node find(int value){
+        Node node = head;
+        while(node != null){
+            if(node.value == value)
+                return node;
+            node = node.next;
+        }
+        return null;
+    }
+
+    // To return a node at a particular index.
+    public Node get(int index){
+        Node node = head;
+        for (int i = 0; i < index; i++) {
+            node = node.next;
+        }
+        return node;
+    }
+
+    // Displaying the entire linked list.
+    public void displayList(){
+        Node temp = head;
+        while(temp != null) {
+            System.out.print(temp.value + "-->");
+            temp = temp.next;
+        }
+        System.out.println("END");
+    }
+}