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

Last Updated : 11 Jan, 2023

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

Algorithm:

The task can be accomplished as:

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.

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.

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.

If node to be inserted has value in between the value of first and last node, then check for appropriate position and make connections.

Implementation:

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

Time complexity: O(n) since using a single loop to traverse doubly linked list
Auxiliary Space: O(1)

Insert value in sorted way in a sorted doubly linked list

AmishTandon

Improve

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

C++

C

Java

Python

C#

Javascript

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