[Solved] Insert a node at a specific position in a linked list solution in Hackerrank - Hacerrank solution C, C++, java,js, Python

Algorithm

Problem Name: Data Structures - Insert a node at a specific position in a linked list

Problem Link: https://www.hackerrank.com/challenges/insert-a-node-at-a-specific-position-in-a-linked-list/problem?isFullScreen=true

In this HackerRank in Data Structures - Insert a node at a specific position in a linked list solutions

Given the pointer to the head node of a linked list and an integer to insert at a certain position, create a new node with the given integer as its data

attribute, insert this node at the desired position and return the head node.

A position of 0 indicates head, a position of 1 indicates one node away from the head and so on. The head pointer given may be null meaning that the initial list is empty.

Example

head refers to the first node in the list 1 -> 2 -> 3

data = 4

position = 2

Insert a node at position 2 with data = 4 The new list is 1 -> 2 -> 4 -> 3

Function Description Complete the function insertNodeAtPosition in the editor below. It must return a reference to the head node of your finished list.

insertNodeAtPosition has the following parameters:

head: a SinglyLinkedListNode pointer to the head of the list
data: an integer value to insert as data in your new node
position: an integer position to insert the new node, zero based indexing

Returns

SinglyLinkedListNode pointer: a reference to the head of the revised list

Input Format

The first line contains an integer n the number of elements in the linked list.
Each of the next n lines contains an integer SinglyLinkedListNode[i].data.
The next line contains an integer data the data of the node that is to be inserted.
The last line contains an integer position.

Constraints

1 <= n <= 1000
1 <= SinglyLinkedList Node[i].data <= 1000, where SinglyLinkedList Node[i] is the i**th element of the linked list.
0 <= position <= n

Sample Input

Sample Output

16 13 1 7

Explanation

The initial linked list is 16 -> 13 -> 7. Insert 1 at the position 2 which currently has 7 in it. The updated linked list is 16 -> 13 -> 1 -> 7.

Code Examples

#1 Code Example with C Programming

Code - 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 SinglyLinkedListNode SinglyLinkedListNode;
typedef struct SinglyLinkedList SinglyLinkedList;

struct SinglyLinkedListNode {
    int data;
    SinglyLinkedListNode* next;
};

struct SinglyLinkedList {
    SinglyLinkedListNode* head;
    SinglyLinkedListNode* tail;
};

SinglyLinkedListNode* create_singly_linked_list_node(int node_data) {
    SinglyLinkedListNode* node = malloc(sizeof(SinglyLinkedListNode));

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

    return node;
}

void insert_node_into_singly_linked_list(SinglyLinkedList** singly_linked_list, int node_data) {
    SinglyLinkedListNode* node = create_singly_linked_list_node(node_data);

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

    (*singly_linked_list)->tail = node;
}

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

        node = node->next;

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

void free_singly_linked_list(SinglyLinkedListNode* node) {
    while (node) {
        SinglyLinkedListNode* temp = node;
        node = node->next;

        free(temp);
    }
}

/*
 * Complete the 'insertNodeAtPosition' function below.
 *
 * The function is expected to return an INTEGER_SINGLY_LINKED_LIST.
 * The function accepts following parameters:
 *  1. INTEGER_SINGLY_LINKED_LIST llist
 *  2. INTEGER data
 *  3. INTEGER position
 */

/*
 * For your reference:
 *
 * SinglyLinkedListNode {
 *     int data;
 *     SinglyLinkedListNode* next;
 * };
 *
 */

SinglyLinkedListNode* insertNodeAtPosition(SinglyLinkedListNode* head, int data, int position) {
    SinglyLinkedListNode* temp = (SinglyLinkedListNode*)malloc(sizeof(SinglyLinkedListNode));
    if(head == NULL) {
        head->data = data;
        head->next = NULL;
        return head;
    } else {
        if(position == 0) {
            temp->data = data;
            temp->next = head;
            return temp;
        } else {
            SinglyLinkedListNode* prev = head;
            temp->data = data;
            for(int i = 0; i < position-1; i++> {
                prev = prev->next;
            }
            temp->next = prev->next;
            prev->next = temp;
        }
    }
    return head;
}


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

    SinglyLinkedList* llist = malloc(sizeof(SinglyLinkedList));
    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_singly_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); }

    char* position_endptr;
    char* position_str = readline();
    int position = strtol(position_str, &position_endptr, 10);

    if (position_endptr == position_str || *position_endptr != '\0') { exit(EXIT_FAILURE); }

    SinglyLinkedListNode* llist_head = insertNodeAtPosition(llist->head, data, position);

    char *sep = " ";

    print_singly_linked_list(llist_head, sep, fptr);
    fprintf(fptr, "\n");

    free_singly_linked_list(llist_head);

    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;
}

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#2 Code Example with C++ Programming

Code - C++ Programming


#include <bits/stdc++.h>

using namespace std;

class SinglyLinkedListNode {
    public:
        int data;
        SinglyLinkedListNode *next;

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

class SinglyLinkedList {
    public:
        SinglyLinkedListNode *head;
        SinglyLinkedListNode *tail;

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

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

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

            this->tail = node;
        }
};

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

        node = node->next;

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

void free_singly_linked_list(SinglyLinkedListNode* node) {
    while (node) {
        SinglyLinkedListNode* temp = node;
        node = node->next;

        free(temp);
    }
}


SinglyLinkedListNode* insertNodeAtPosition(SinglyLinkedListNode* head, int data, int position) {
SinglyLinkedListNode *temp=new SinglyLinkedListNode(data);
SinglyLinkedListNode *nh= head;
for(int i=0;i < position-1;i++)
{
    nh=nh->next;
}
SinglyLinkedListNode *t;
t=nh->next ;
nh->next=temp;
temp->next=t;
return head;
}
int main()
{
    ofstream fout(getenv("OUTPUT_PATH"));

    SinglyLinkedList* llist = new SinglyLinkedList();

    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');

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

    SinglyLinkedListNode* llist_head = insertNodeAtPosition(llist->head, data, position);

    print_singly_linked_list(llist_head, " ", fout);
    fout << "\n";

    free_singly_linked_list(llist_head);

    fout.close();

    return 0;
}

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#3 Code Example with Java Programming

Code - 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 SinglyLinkedListNode {
        public int data;
        public SinglyLinkedListNode next;

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

    static class SinglyLinkedList {
        public SinglyLinkedListNode head;
        public SinglyLinkedListNode tail;

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

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

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

            this.tail = node;
        }
    }

    public static void printSinglyLinkedList(SinglyLinkedListNode 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);
            }
        }
    }

    
static SinglyLinkedListNode insertNodeAtPosition(SinglyLinkedListNode head, int data, int position) {
        if (head == null) return null;
        SinglyLinkedListNode temp = new SinglyLinkedListNode(data);
        if (position == 0) {
            temp.next = head;
            return temp;
        }
        SinglyLinkedListNode p = head;
        for (int i = 0; i <  position-1; i++) {
            p = p.next;
        }
        SinglyLinkedListNode next = p.next;
        p.next = temp;
        temp.next = next;
        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")));

        SinglyLinkedList llist = new SinglyLinkedList();

        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])?");

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

        SinglyLinkedListNode llist_head = insertNodeAtPosition(llist.head, data, position);

        printSinglyLinkedList(llist_head, " ", bufferedWriter);
        bufferedWriter.newLine();

        bufferedWriter.close();

        scanner.close();
    }
}

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#4 Code Example with Python Programming

Code - Python Programming


#!/bin/python3

import math
import os
import random
import re
import sys

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

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

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

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


        self.tail = node

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

        node = node.next

        if node:
            fptr.write(sep)

#
# Complete the 'insertNodeAtPosition' function below.
#
# The function is expected to return an INTEGER_SINGLY_LINKED_LIST.
# The function accepts following parameters:
#  1. INTEGER_SINGLY_LINKED_LIST llist
#  2. INTEGER data
#  3. INTEGER position
#

#
# For your reference:
#
# SinglyLinkedListNode:
#     int data
#     SinglyLinkedListNode next
#
#

class Node(object):
 
    def __init__(self, data=None, next_node=None):
       self.data = data
       self.next = next_node

def insertNodeAtPosition(head, data, position):
    if position==0:
        head = Node(data,head)
        return head
    else:
        temp_head = head
        while position>1:
            temp_head = temp_head.next
            position = position -1
        temp_head.next = Node(data,temp_head.next)
        return head

if __name__ == '__main__':

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Demonstration

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