Viral Advertising – HackerRank Solution

In this post, we will solve Viral Advertising HackerRank Solution. This problem (Viral Advertising) is a part of HackerRank Algorithms series.


HackerLand Enterprise is adopting a new viral advertising strategy. When they launch a new product, they advertise it to exactly 5 people on social media.

On the first day, half of those 5 people (i.e., floor(5/2) = 2) like the advertisement and each shares it with 3 of their friends. At the beginning of the second day, floor(5/2) x 3 = 2 x 3 = 6 people receive the advertisement.

Each day, floor(recipients/2) of the recipients like the advertisement and will share it with 3 friends on the following day. Assuming nobody receives the advertisement twice, determine how many people have liked the ad by the end of a given day, beginning with launch day as day 1.

n = 5.

Day Shared Liked Cumulative
1      5     2       2
2      6     3       5
3      9     4       9
4     12     6      15
5     18     9      24

The progression is shown above. The cumulative number of likes on the 5th day is 24.

Function Description

Complete the viralAdvertising function in the editor below.

viralAdvertising has the following parameter(s):

  • int n: the day number to report


  • int: the cumulative likes at that day

Input Format

A single integer, n, the day number.


  • 1 <= n <= 50

Sample Input


Sample Output



2 people liked the advertisement on the first day, 3 people liked the advertisement on the second day and 4 people liked the advertisement on the third day, so the answer is 2 + 3 + 4 =9.

Solution – Viral Advertising – HackerRank Solution


#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;

int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    int n;
    int m = 5;
    int total;
    for(int i=0; i<n; ++i){
        m = m/2;
        total += m;
        m *= 3;
    return 0;



import math
import os
import random
import re
import sys

# Complete the viralAdvertising function below.
def viralAdvertising(n):
    shared =5
    for i in range(1,n+1):
        liked = shared//2
        shared = liked*3
    return cumulative

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

    n = int(input())

    result = viralAdvertising(n)

    fptr.write(str(result) + '\n')



import java.util.*;

public class Solution {

    public static final int INITIAL_AMOUNT_OF_PEOPLE = 5;

    public static void main(String[] args) {
        try (Scanner scanner = new Scanner( {
            int n = scanner.nextInt();
            int currentAmount = INITIAL_AMOUNT_OF_PEOPLE;
            int totalNumber = 0;
            for (int i = 0; i < n; i++) {
                currentAmount = currentAmount/2;
                totalNumber += currentAmount;
                currentAmount *= 3;

Note: This problem (Viral Advertising) is generated by HackerRank but the solution is provided by CodingBroz. This tutorial is only for Educational and Learning purpose.

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