HackerRank•Jun 08, 2025

Print in Reverse

Hazrat Ali

HackerRank

Given a pointer to the head of a singly-linked list, print each  value from the reversed list. If the given list is empty, do not print anything.

Example

 refers to the linked list with  values 

Print the following:
3
2
1

Function Description

Complete the reversePrint function in the editor below.

reversePrint has the following parameters:

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

Prints

The  values of each node in the reversed list.

Input Format

The first line of input contains , the number of test cases.

The input of each test case is as follows:

  • The first line contains an integer , the number of elements in the list.
  • Each of the next n lines contains a data element for a list node.

Constraints

  • , where  is the  element in the list.

Sample Input

3
5
16
12
4
2
5
3
7
3
9
5
5
1
18
3
13

Sample Output

5
2
4
12
16
9
3
7
13
3
18
1
5

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;
        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) {
    while (node) {
        cout << node->data;

        node = node->next;

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

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

        free(temp);
    }
}

/*
 * Complete the 'reversePrint' function below.
 *
 * The function accepts INTEGER_SINGLY_LINKED_LIST llist as parameter.
 */

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

void reversePrint(SinglyLinkedListNode* head) {
    if (!head) return;
    reversePrint(head->next);
    cout << head->data << endl;
}

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

    for (int tests_itr = 0; tests_itr < tests; tests_itr++) {
        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);
        }

        reversePrint(llist->head);
    }

    return 0;
}




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