HackerRank•Jun 11, 2025

Insert a Node at the Tail of a Linked List

Hazrat Ali

HackerRank

You are given the pointer to the head node of a linked list and an integer to add to the list. Create a new node with the given integer. Insert this node at the tail of the linked list and return the head node of the linked list formed after inserting this new node. The given head pointer may be null, meaning that the initial list is empty.

Function Description

Complete the  function with the following parameters:

  • : a reference to the head of a list
  • : the data value for the node to insert

Returns

  • : reference to the head of the modified linked list

Input Format

The first line contains an integer , the number of elements in the linked list.
The next  lines contain an integer each, the value that needs to be inserted at tail.

Sample Input

STDIN   Function
-----   --------
5       size of linked list n = 5
141     linked list data values 141..474
302
164
530
474

Sample Output

141
302
164
530
474





Solution
#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;

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

};

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);
    }
}

// Complete the insertNodeAtTail function below.

/*
 * For your reference:
 *
 * SinglyLinkedListNode {
 *     int data;
 *     SinglyLinkedListNode* next;
 * };
 *
 */
SinglyLinkedListNode* insertNodeAtTail(SinglyLinkedListNode* head, int data) {

SinglyLinkedListNode* node = new SinglyLinkedListNode(data);

    if (head == nullptr) return node;

    SinglyLinkedListNode* temp = head;

    while (temp->next != nullptr)
        temp = temp->next;

    temp->next = node;
    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');
   
        SinglyLinkedListNode* llist_head = insertNodeAtTail(llist->head, llist_item);
        llist->head = llist_head;
    }

    print_singly_linked_list(llist->head, "\n", fout);
    fout << "\n";

    free_singly_linked_list(llist->head);

    fout.close();

    return 0;
}








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