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Sorted insert in a doubly linked list with head and tail pointers

  • Difficulty Level : Easy
  • Last Updated : 03 Jun, 2021

A Doubly linked list is a linked list that consists of a set of sequentially linked records called nodes. Each node contains two fields that are references to the previous and to the next node in the sequence of nodes.
The task is to create a doubly linked list by inserting nodes such that list remains in ascending order on printing from left to right. Also, we need to maintain two pointers, head (points to first node) and tail (points to last node).
Examples: 
 

Input : 40 50 10 45 90 100 95
Output :10 40 45 50 90 95 100

Input : 30 10 50 43 56 12
Output :10 12 30 43 50 56

 

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Algorithm: 
The task can be accomplished as: 
 

  1. If Linked list is empty then make both the left and right pointers point to the node to be inserted and make its previous and next field point to NULL.
  2. If node to be inserted has value less than the value of first node of linked list then connect that node from previous field of first node.
  3. If node to be inserted has value more than the value of last node of linked list then connect that node from next field of last node.
  4. If node to be inserted has value in between the value of first and last node, then check for appropriate position and make connections.

 

C++




/* C++ program to insetail nodes in doubly
linked list such that list remains in
ascending order on printing from left
to right */
#include <bits/stdc++.h>
using namespace std;
 
// A linked list node
class Node
{
    public:
    Node *prev;
    int info;
    Node *next;
};
 
// Function to insetail new node
void nodeInsetail(Node **head,
                Node **tail,
                int key)
{
 
    Node *p = new Node();
    p->info = key;
    p->next = NULL;
 
    // If first node to be insetailed in doubly
    // linked list
    if ((*head) == NULL)
    {
        (*head) = p;
        (*tail) = p;
        (*head)->prev = NULL;
        return;
    }
 
    // If node to be insetailed has value less
    // than first node
    if ((p->info) < ((*head)->info))
    {
        p->prev = NULL;
        (*head)->prev = p;
        p->next = (*head);
        (*head) = p;
        return;
    }
 
    // If node to be insetailed has value more
    // than last node
    if ((p->info) > ((*tail)->info))
    {
        p->prev = (*tail);
        (*tail)->next = p;
        (*tail) = p;
        return;
    }
 
    // Find the node before which we need to
    // insert p.
    Node *temp = (*head)->next;
    while ((temp->info) < (p->info))
        temp = temp->next;
 
    // Insert new node before temp
    (temp->prev)->next = p;
    p->prev = temp->prev;
    temp->prev = p;
    p->next = temp;
}
 
// Function to print nodes in from left to right
void printList(Node *temp)
{
    while (temp != NULL)
    {
        cout << temp->info << " ";
        temp = temp->next;
    }
}
 
// Driver program to test above functions
int main()
{
    Node *left = NULL, *right = NULL;
    nodeInsetail(&left, &right, 30);
    nodeInsetail(&left, &right, 50);
    nodeInsetail(&left, &right, 90);
    nodeInsetail(&left, &right, 10);
    nodeInsetail(&left, &right, 40);
    nodeInsetail(&left, &right, 110);
    nodeInsetail(&left, &right, 60);
    nodeInsetail(&left, &right, 95);
    nodeInsetail(&left, &right, 23);
 
    cout<<"Doubly linked list on printing"
        " from left to right\n";
    printList(left);
 
    return 0;
}
 
// This is code is contributed by rathbhupendra

C




/* C program to insetail nodes in doubly
linked list such that list remains in
ascending order on printing from left
to right */
#include<stdio.h>
#include<stdlib.h>
 
// A linked list node
struct Node
{
    struct Node *prev;
    int info;
    struct Node *next;
};
 
// Function to insetail new node
void nodeInsetail(struct Node **head,
                  struct Node **tail,
                  int key)
{
 
    struct Node *p = new Node;
    p->info = key;
    p->next = NULL;
 
    // If first node to be insetailed in doubly
    // linked list
    if ((*head) == NULL)
    {
        (*head) = p;
        (*tail) = p;
        (*head)->prev = NULL;
        return;
    }
 
    // If node to be insetailed has value less
    // than first node
    if ((p->info) < ((*head)->info))
    {
        p->prev = NULL;
        (*head)->prev = p;
        p->next = (*head);
        (*head) = p;
        return;
    }
 
    // If node to be insetailed has value more
    // than last node
    if ((p->info) > ((*tail)->info))
    {
        p->prev = (*tail);
        (*tail)->next = p;
        (*tail) = p;
        return;
    }
 
    // Find the node before which we need to
    // insert p.
    temp = (*head)->next;
    while ((temp->info) < (p->info))
        temp = temp->next;
 
    // Insert new node before temp
    (temp->prev)->next = p;
    p->prev = temp->prev;
    temp->prev = p;
    p->next = temp;
}
 
// Function to print nodes in from left to right
void printList(struct Node *temp)
{
    while (temp != NULL)
    {
        printf("%d ", temp->info);
        temp = temp->next;
    }
}
 
// Driver program to test above functions
int main()
{
    struct Node *left = NULL, *right = NULL;
    nodeInsetail(&left, &right, 30);
    nodeInsetail(&left, &right, 50);
    nodeInsetail(&left, &right, 90);
    nodeInsetail(&left, &right, 10);
    nodeInsetail(&left, &right, 40);
    nodeInsetail(&left, &right, 110);
    nodeInsetail(&left, &right, 60);
    nodeInsetail(&left, &right, 95);
    nodeInsetail(&left, &right, 23);
 
    printf("\nDoubly linked list on printing"
           " from left to right\n");
    printList(left);
 
    return 0;
}

Java




/* Java program to insetail nodes in doubly
linked list such that list remains in
ascending order on printing from left
to right */
 
import java.io.*;
import java.util.*;
 
// A linked list node
class Node
{
    int info;
    Node prev, next;
}
 
class GFG
{
 
    static Node head, tail;
 
    // Function to insetail new node
    static void nodeInsetail(int key)
    {
        Node p = new Node();
        p.info = key;
        p.next = null;
 
        // If first node to be insetailed in doubly
        // linked list
        if (head == null)
        {
            head = p;
            tail = p;
            head.prev = null;
            return;
        }
 
        // If node to be insetailed has value less
        // than first node
        if (p.info < head.info)
        {
            p.prev = null;
            head.prev = p;
            p.next = head;
            head = p;
            return;
        }
             
        // If node to be insetailed has value more
        // than last node
        if (p.info > tail.info)
        {
            p.prev = tail;
            tail.next = p;
            tail = p;
            return;
        }
 
        // Find the node before which we need to
        // insert p.
        Node temp = head.next;
        while (temp.info < p.info)
                temp = temp.next;
                 
        // Insert new node before temp
        (temp.prev).next = p;
        p.prev = temp.prev;
        temp.prev = p;
        p.next = temp;
    }
 
    // Function to print nodes in from left to right
    static void printList(Node temp)
    {
        while (temp != null)
        {
                System.out.print(temp.info + " ");
                temp = temp.next;
        }
    }
 
    // Driver code
    public static void main(String args[])
    {
        head = tail = null;
        nodeInsetail(30);
        nodeInsetail(50);
        nodeInsetail(90);
        nodeInsetail(10);
        nodeInsetail(40);
        nodeInsetail(110);
        nodeInsetail(60);
        nodeInsetail(95);
        nodeInsetail(23);
 
        System.out.println("Doubly linked list on printing from left to right");
        printList(head);
    }
}
 
// This code is contributed by rachana soma

Python




# Python program to insetail nodes in doubly
# linked list such that list remains in
# ascending order on printing from left
# to right
 
# Linked List node
class Node:
    def __init__(self, data):
        self.info = data
        self.next = None
        self.prev = None
 
head = None
tail = None
                 
# Function to insetail new node
def nodeInsetail( key) :
 
    global head
    global tail
     
    p = Node(0)
    p.info = key
    p.next = None
 
    # If first node to be insetailed in doubly
    # linked list
    if ((head) == None) :
        (head) = p
        (tail) = p
        (head).prev = None
        return
     
    # If node to be insetailed has value less
    # than first node
    if ((p.info) < ((head).info)) :
        p.prev = None
        (head).prev = p
        p.next = (head)
        (head) = p
        return
 
    # If node to be insetailed has value more
    # than last node
    if ((p.info) > ((tail).info)) :
     
        p.prev = (tail)
        (tail).next = p
        (tail) = p
        return
     
    # Find the node before which we need to
    # insert p.
    temp = (head).next
    while ((temp.info) < (p.info)) :
        temp = temp.next
 
    # Insert new node before temp
    (temp.prev).next = p
    p.prev = temp.prev
    temp.prev = p
    p.next = temp
 
# Function to print nodes in from left to right
def printList(temp) :
 
    while (temp != None) :
     
        print( temp.info, end = " ")
        temp = temp.next
     
# Driver program to test above functions
nodeInsetail( 30)
nodeInsetail( 50)
nodeInsetail( 90)
nodeInsetail( 10)
nodeInsetail( 40)
nodeInsetail( 110)
nodeInsetail( 60)
nodeInsetail( 95)
nodeInsetail( 23)
 
print("Doubly linked list on printing from left to right\n" )
 
printList(head)
 
# This code is contributed by Arnab Kundu

C#




/* C# program to insetail nodes in doubly
linked list such that list remains in
ascending order on printing from left
to right */
using System;
 
// A linked list node
public class Node
{
    public int info;
    public Node prev, next;
}
 
class GFG
{
 
    static Node head, tail;
 
    // Function to insetail new node
    static void nodeInsetail(int key)
    {
        Node p = new Node();
        p.info = key;
        p.next = null;
 
        // If first node to be insetailed in doubly
        // linked list
        if (head == null)
        {
            head = p;
            tail = p;
            head.prev = null;
            return;
        }
 
        // If node to be insetailed has value less
        // than first node
        if (p.info < head.info)
        {
            p.prev = null;
            head.prev = p;
            p.next = head;
            head = p;
            return;
        }
             
        // If node to be insetailed has value more
        // than last node
        if (p.info > tail.info)
        {
            p.prev = tail;
            tail.next = p;
            tail = p;
            return;
        }
 
        // Find the node before which we need to
        // insert p.
        Node temp = head.next;
        while (temp.info < p.info)
            temp = temp.next;
                 
        // Insert new node before temp
        (temp.prev).next = p;
        p.prev = temp.prev;
        temp.prev = p;
        p.next = temp;
    }
 
    // Function to print nodes in from left to right
    static void printList(Node temp)
    {
        while (temp != null)
        {
            Console.Write(temp.info + " ");
            temp = temp.next;
        }
    }
 
    // Driver code
    public static void Main(String []args)
    {
        head = tail = null;
        nodeInsetail(30);
        nodeInsetail(50);
        nodeInsetail(90);
        nodeInsetail(10);
        nodeInsetail(40);
        nodeInsetail(110);
        nodeInsetail(60);
        nodeInsetail(95);
        nodeInsetail(23);
 
        Console.WriteLine("Doubly linked list on printing from left to right");
        printList(head);
    }
}
 
// This code is contributed by Arnab Kundu

Javascript




<script>
/* javascript program to insetail nodes in doubly
linked list such that list remains in
ascending order on printing from left
to right */
 
// A linked list node
 class Node {
        constructor() {
            this.info = 0;
            this.prev = null;
            this.next = null;
        }
    }
var head, tail;
 
    // Function to insetail new node
    function nodeInsetail(key) {
         p = new Node();
        p.info = key;
        p.next = null;
 
        // If first node to be insetailed in doubly
        // linked list
        if (head == null) {
            head = p;
            tail = p;
            head.prev = null;
            return;
        }
 
        // If node to be insetailed has value less
        // than first node
        if (p.info < head.info) {
            p.prev = null;
            head.prev = p;
            p.next = head;
            head = p;
            return;
        }
 
        // If node to be insetailed has value more
        // than last node
        if (p.info > tail.info) {
            p.prev = tail;
            tail.next = p;
            tail = p;
            return;
        }
 
        // Find the node before which we need to
        // insert p.
         temp = head.next;
        while (temp.info < p.info)
            temp = temp.next;
 
        // Insert new node before temp
        (temp.prev).next = p;
        p.prev = temp.prev;
        temp.prev = p;
        p.next = temp;
    }
 
    // Function to print nodes in from left to right
    function printList( temp) {
        while (temp != null) {
            document.write(temp.info + " ");
            temp = temp.next;
        }
    }
 
    // Driver code
     
        head = tail = null;
        nodeInsetail(30);
        nodeInsetail(50);
        nodeInsetail(90);
        nodeInsetail(10);
        nodeInsetail(40);
        nodeInsetail(110);
        nodeInsetail(60);
        nodeInsetail(95);
        nodeInsetail(23);
 
        document.write("Doubly linked list on printing from left to right<br/>");
        printList(head);
 
// This code is contributed by aashish1995
</script>
Output: 
Doubly linked list on printing from left to right
10 23 30 40 50 60 90 95 110

 




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