In this HackerRank Inserting a Node into a sorted doubly linked list Interview preparation kit problem You have Given a reference to the head of a doubly-linked list and an integer, data, create a new DoublyLinkedListNode object having data value data and insert it at the proper location to maintain the sort.


HackerRank Inserting a Node Into a Sorted Doubly Linked List solution


Problem solution in Python programming.

#!/bin/python3

import math
import os
import random
import re
import sys

class DoublyLinkedListNode:
    def __init__(self, node_data):
        self.data = node_data
        self.next = None
        self.prev = None

class DoublyLinkedList:
    def __init__(self):
        self.head = None
        self.tail = None

    def insert_node(self, node_data):
        node = DoublyLinkedListNode(node_data)

        if not self.head:
            self.head = node
        else:
            self.tail.next = node
            node.prev = self.tail


        self.tail = node

def print_doubly_linked_list(node, sep, fptr):
    while node:
        fptr.write(str(node.data))

        node = node.next

        if node:
            fptr.write(sep)

# Complete the sortedInsert function below.

#
# For your reference:
#
# DoublyLinkedListNode:
#     int data
#     DoublyLinkedListNode next
#     DoublyLinkedListNode prev
#
#
def sortedInsert(head, data):
    cur=head
    node=DoublyLinkedListNode(data)
    if cur.data>data or cur.data==data:
        node.next=cur
        cur.prev=node
        head=node
        return head
    while cur.next:
        if (cur.data<data and cur.next.data>data) or cur.data==data:
            node.next=cur.next
            cur.next.prev=node
            node.prev=cur
            cur.next=node
            return head
        cur=cur.next
    if cur.data<data or cur.data==data:
        node.prev=cur
        cur.next=node
        return head

if __name__ == '__main__':
    fptr = open(os.environ['OUTPUT_PATH'], 'w')

    t = int(input())

    for t_itr in range(t):
        llist_count = int(input())

        llist = DoublyLinkedList()

        for _ in range(llist_count):
            llist_item = int(input())
            llist.insert_node(llist_item)

        data = int(input())

        llist1 = sortedInsert(llist.head, data)

        print_doubly_linked_list(llist1, ' ', fptr)
        fptr.write('\n')

    fptr.close()


Problem solution in Java Programming.

import java.io.*;
import java.math.*;
import java.security.*;
import java.text.*;
import java.util.*;
import java.util.concurrent.*;
import java.util.regex.*;

public class Solution {

    static class DoublyLinkedListNode {
        public int data;
        public DoublyLinkedListNode next;
        public DoublyLinkedListNode prev;

        public DoublyLinkedListNode(int nodeData) {
            this.data = nodeData;
            this.next = null;
            this.prev = null;
        }
    }

    static class DoublyLinkedList {
        public DoublyLinkedListNode head;
        public DoublyLinkedListNode tail;

        public DoublyLinkedList() {
            this.head = null;
            this.tail = null;
        }

        public void insertNode(int nodeData) {
            DoublyLinkedListNode node = new DoublyLinkedListNode(nodeData);

            if (this.head == null) {
                this.head = node;
            } else {
                this.tail.next = node;
                node.prev = this.tail;
            }

            this.tail = node;
        }
    }

    public static void printDoublyLinkedList(DoublyLinkedListNode node, String sep, BufferedWriter bufferedWriter) throws IOException {
        while (node != null) {
            bufferedWriter.write(String.valueOf(node.data));

            node = node.next;

            if (node != null) {
                bufferedWriter.write(sep);
            }
        }
    }

    // Complete the sortedInsert function below.

    /*
     * For your reference:
     *
     * DoublyLinkedListNode {
     *     int data;
     *     DoublyLinkedListNode next;
     *     DoublyLinkedListNode prev;
     * }
     *
     */
    static DoublyLinkedListNode sortedInsert(DoublyLinkedListNode head, int data) {
        DoublyLinkedListNode node = new DoublyLinkedListNode(data);
        if (head == null) {
            return node;
        } else if (data <= head.data) {
            node.next = head;
            head.prev = node;
            return node;
        } else {
            DoublyLinkedListNode ptr = sortedInsert(head.next, data);
            head.next = ptr;
            ptr.prev = head;
            return head;
        }
    }

    private static final Scanner scanner = new Scanner(System.in);

    public static void main(String[] args) throws IOException {
        BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(System.getenv("OUTPUT_PATH")));

        int t = scanner.nextInt();
        scanner.skip("(\r\n|[\n\r\u2028\u2029\u0085])?");

        for (int tItr = 0; tItr < t; tItr++) {
            DoublyLinkedList llist = new DoublyLinkedList();

            int llistCount = scanner.nextInt();
            scanner.skip("(\r\n|[\n\r\u2028\u2029\u0085])?");

            for (int i = 0; i < llistCount; i++) {
                int llistItem = scanner.nextInt();
                scanner.skip("(\r\n|[\n\r\u2028\u2029\u0085])?");

                llist.insertNode(llistItem);
            }

            int data = scanner.nextInt();
            scanner.skip("(\r\n|[\n\r\u2028\u2029\u0085])?");

            DoublyLinkedListNode llist1 = sortedInsert(llist.head, data);

            printDoublyLinkedList(llist1, " ", bufferedWriter);
            bufferedWriter.newLine();
        }

        bufferedWriter.close();

        scanner.close();
    }
}

Problem solution in C++ programming.

#include <bits/stdc++.h>

using namespace std;

class DoublyLinkedListNode {
    public:
        int data;
        DoublyLinkedListNode *next;
        DoublyLinkedListNode *prev;

        DoublyLinkedListNode(int node_data) {
            this->data = node_data;
            this->next = nullptr;
            this->prev = nullptr;
        }
};

class DoublyLinkedList {
    public:
        DoublyLinkedListNode *head;
        DoublyLinkedListNode *tail;

        DoublyLinkedList() {
            this->head = nullptr;
            this->tail = nullptr;
        }

        void insert_node(int node_data) {
            DoublyLinkedListNode* node = new DoublyLinkedListNode(node_data);

            if (!this->head) {
                this->head = node;
            } else {
                this->tail->next = node;
                node->prev = this->tail;
            }

            this->tail = node;
        }
};

void print_doubly_linked_list(DoublyLinkedListNode* node, string sep, ofstream& fout) {
    while (node) {
        fout << node->data;

        node = node->next;

        if (node) {
            fout << sep;
        }
    }
}

void free_doubly_linked_list(DoublyLinkedListNode* node) {
    while (node) {
        DoublyLinkedListNode* temp = node;
        node = node->next;

        free(temp);
    }
}

// Complete the sortedInsert function below.

/*
 * For your reference:
 *
 * DoublyLinkedListNode {
 *     int data;
 *     DoublyLinkedListNode* next;
 *     DoublyLinkedListNode* prev;
 * };
 *
 */
DoublyLinkedListNode* sortedInsert(DoublyLinkedListNode* head, int data) {

  DoublyLinkedListNode* node = new DoublyLinkedListNode(data);
  
  node->data = data;
  node->next = node->prev = NULL;
  
  if(head==NULL)
   return node;
   

 if(head->data > data){
     head->prev = node;
     node->next = head;
     return node;
 }
 
 DoublyLinkedListNode* next = sortedInsert(head->next, data);
 head->next = next;
 next->prev = head;
 return head;

}

int main()
{
    ofstream fout(getenv("OUTPUT_PATH"));

    int t;
    cin >> t;
    cin.ignore(numeric_limits<streamsize>::max(), '\n');

    for (int t_itr = 0; t_itr < t; t_itr++) {
        DoublyLinkedList* llist = new DoublyLinkedList();

        int llist_count;
        cin >> llist_count;
        cin.ignore(numeric_limits<streamsize>::max(), '\n');

        for (int i = 0; i < llist_count; i++) {
            int llist_item;
            cin >> llist_item;
            cin.ignore(numeric_limits<streamsize>::max(), '\n');

            llist->insert_node(llist_item);
        }

        int data;
        cin >> data;
        cin.ignore(numeric_limits<streamsize>::max(), '\n');

        DoublyLinkedListNode* llist1 = sortedInsert(llist->head, data);

        print_doubly_linked_list(llist1, " ", fout);
        fout << "\n";

        free_doubly_linked_list(llist1);
    }

    fout.close();

    return 0;
}


Problem solution in C programming.

#include <assert.h>
#include <limits.h>
#include <math.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

char* readline();

typedef struct DoublyLinkedListNode DoublyLinkedListNode;
typedef struct DoublyLinkedList DoublyLinkedList;

struct DoublyLinkedListNode {
    int data;
    DoublyLinkedListNode* next;
    DoublyLinkedListNode* prev;
};

struct DoublyLinkedList {
    DoublyLinkedListNode* head;
    DoublyLinkedListNode* tail;
};

DoublyLinkedListNode* create_doubly_linked_list_node(int node_data) {
    DoublyLinkedListNode* node = malloc(sizeof(DoublyLinkedListNode));

    node->data = node_data;
    node->next = NULL;
    node->prev = NULL;

    return node;
}

void insert_node_into_doubly_linked_list(DoublyLinkedList** doubly_linked_list, int node_data) {
    DoublyLinkedListNode* node = create_doubly_linked_list_node(node_data);

    if (!(*doubly_linked_list)->head) {
        (*doubly_linked_list)->head = node;
    } else {
        (*doubly_linked_list)->tail->next = node;
        node->prev = (*doubly_linked_list)->tail;
    }

    (*doubly_linked_list)->tail = node;
}

void print_doubly_linked_list(DoublyLinkedListNode* node, char* sep, FILE* fptr) {
    while (node) {
        fprintf(fptr, "%d", node->data);

        node = node->next;

        if (node) {
            fprintf(fptr, "%s", sep);
        }
    }
}

void free_doubly_linked_list(DoublyLinkedListNode* node) {
    while (node) {
        DoublyLinkedListNode* temp = node;
        node = node->next;

        free(temp);
    }
}

// Complete the sortedInsert function below.

/*
 * For your reference:
 *
 * DoublyLinkedListNode {
 *     int data;
 *     DoublyLinkedListNode* next;
 *     DoublyLinkedListNode* prev;
 * };
 *
 */
DoublyLinkedListNode* sortedInsert(DoublyLinkedListNode* head, int data) {
    DoublyLinkedListNode *new = create_doubly_linked_list_node(data);
    if (head == NULL) return new;
    if (new->data <= head->data) { // Insert at head of list
        new->next = head;
        head->prev = new;
        return new;
    }
    
    DoublyLinkedListNode *curr = head;
    while (curr->next != NULL && curr->next->data < new->data) {
        curr = curr->next;
    }
    
    if (curr->next == NULL) { // Insert at end of list
        curr->next = new;
        new->prev = curr;
    } else { // Insert somewhere in the middle
        new->next = curr->next;
        curr->next->prev = curr;
        curr->next = new;
    }
    return head;

}

int main()
{
    FILE* fptr = fopen(getenv("OUTPUT_PATH"), "w");

    char* t_endptr;
    char* t_str = readline();
    int t = strtol(t_str, &t_endptr, 10);

    if (t_endptr == t_str || *t_endptr != '\0') { exit(EXIT_FAILURE); }

    for (int t_itr = 0; t_itr < t; t_itr++) {
        DoublyLinkedList* llist = malloc(sizeof(DoublyLinkedList));
        llist->head = NULL;
        llist->tail = NULL;

        char* llist_count_endptr;
        char* llist_count_str = readline();
        int llist_count = strtol(llist_count_str, &llist_count_endptr, 10);

        if (llist_count_endptr == llist_count_str || *llist_count_endptr != '\0') { exit(EXIT_FAILURE); }

        for (int i = 0; i < llist_count; i++) {
            char* llist_item_endptr;
            char* llist_item_str = readline();
            int llist_item = strtol(llist_item_str, &llist_item_endptr, 10);

            if (llist_item_endptr == llist_item_str || *llist_item_endptr != '\0') { exit(EXIT_FAILURE); }

            insert_node_into_doubly_linked_list(&llist, llist_item);
        }

        char* data_endptr;
        char* data_str = readline();
        int data = strtol(data_str, &data_endptr, 10);

        if (data_endptr == data_str || *data_endptr != '\0') { exit(EXIT_FAILURE); }

        DoublyLinkedListNode* llist1 = sortedInsert(llist->head, data);

        char *sep = " ";

        print_doubly_linked_list(llist1, sep, fptr);
        fprintf(fptr, "\n");

        free_doubly_linked_list(llist1);
    }

    fclose(fptr);

    return 0;
}

char* readline() {
    size_t alloc_length = 1024;
    size_t data_length = 0;
    char* data = malloc(alloc_length);

    while (true) {
        char* cursor = data + data_length;
        char* line = fgets(cursor, alloc_length - data_length, stdin);

        if (!line) { break; }

        data_length += strlen(cursor);

        if (data_length < alloc_length - 1 || data[data_length - 1] == '\n') { break; }

        size_t new_length = alloc_length << 1;
        data = realloc(data, new_length);

        if (!data) { break; }

        alloc_length = new_length;
    }

    if (data[data_length - 1] == '\n') {
        data[data_length - 1] = '\0';
    }

    data = realloc(data, data_length);

    return data;
}


Problem solution in JavaScript programming.

'use strict';

const fs = require('fs');

process.stdin.resume();
process.stdin.setEncoding('utf-8');

let inputString = '';
let currentLine = 0;

process.stdin.on('data', inputStdin => {
    inputString += inputStdin;
});

process.stdin.on('end', _ => {
    inputString = inputString.replace(/\s*$/, '')
        .split('\n')
        .map(str => str.replace(/\s*$/, ''));

    main();
});

function readLine() {
    return inputString[currentLine++];
}

const DoublyLinkedListNode = class {
    constructor(nodeData) {
        this.data = nodeData;
        this.next = null;
        this.prev = null;
    }
};

const DoublyLinkedList = class {
    constructor() {
        this.head = null;
        this.tail = null;
    }

    insertNode(nodeData) {
        let node = new DoublyLinkedListNode(nodeData);

        if (this.head == null) {
            this.head = node;
        } else {
            this.tail.next = node;
            node.prev = this.tail;
        }

        this.tail = node;
    }
};

function printDoublyLinkedList(node, sep, ws) {
    while (node != null) {
        ws.write(String(node.data));

        node = node.next;

        if (node != null) {
            ws.write(sep);
        }
    }
}

// Complete the sortedInsert function below.

/*
 * For your reference:
 *
 * DoublyLinkedListNode {
 *     int data;
 *     DoublyLinkedListNode next;
 *     DoublyLinkedListNode prev;
 * }
 *
 */
function sortedInsert(head, data) {
    if(head == null) {
        return new DoublyLinkedListNode(data);
    }
    var current = head;
    if(data < current.data) {
        var newNode = new DoublyLinkedListNode(data);
        newNode.next = current;
        current.prev = newNode;
        return newNode;        
    }
    
    while(current != null) {
        if(data >= current.data) {
            if(current.next == null) {
                var newNode = new DoublyLinkedListNode(data);
                current.next = newNode;
                newNode.prev = current;
                
                return head;
            }
            
            if(current.next.data >= data) {
                var newNode = new DoublyLinkedListNode(data);
                newNode.next = current.next;
                newNode.prev = current;
                current.next = newNode;
                newNode.next.prev = newNode;
                
                return head;
            }
        }
        
        current = current.next;
    }
    
    return head;
    
}

function main() {
    const ws = fs.createWriteStream(process.env.OUTPUT_PATH);

    const t = parseInt(readLine(), 10);

    for (let tItr = 0; tItr < t; tItr++) {
        const llistCount = parseInt(readLine(), 10);

        let llist = new DoublyLinkedList();

        for (let i = 0; i < llistCount; i++) {
            const llistItem = parseInt(readLine(), 10);
            llist.insertNode(llistItem);
        }

        const data = parseInt(readLine(), 10);

        let llist1 = sortedInsert(llist.head, data);

        printDoublyLinkedList(llist1, " ", ws)
        ws.write("\n");
    }

    ws.end();
}