HackerRank Viral Advertising Problem Solution

In this post, we will solve HackerRank Viral Advertising Problem. 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) × 3 = 2 × 3 = 6 people receive the advertisement.

Each day, floor( recipients/2 ) of the recipients like the advertisement and will share it with 3 2 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.

Example

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

Returns

int: the cumulative likes at that day

Input Format

A single integer, n, the day number.

Constraints

1 < n < 50

Sample Input

Sample Output

Explanation

This example is depicted in the following diagram:

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.

Table of Contents

Viral Advertising C Solution

#include <stdio.h>
#include <string.h>
#include <math.h>
#include <stdlib.h>

int main() {
    int in, total=2, jour, anciens=2, i;
    scanf("%d", &in); 
    for(jour=2;jour<in+1;jour++){
        anciens = (3*anciens)/2;
        total += anciens;
    }
    printf("%d", total);
    return 0;
}

Viral Advertising C++ Solution

#include <iostream>
#include <vector>
#include <algorithm>
#include <cstring>
#include <queue>
#include <map>
#include <set>
#include <string>
#include <cmath>
#include <cassert>
#include <unordered_set>
#include <unordered_map>

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<pair<int, int>> vpii;
typedef vector<vector<int>> vvi;
typedef vector<vector<pair<int, int>>> vvpii;

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    int n;
    cin >> n;
    int f = 2;
    int ans = 2;
    for (int i = 1; i < n; i++) {
        f = 3*f/2;
        ans += f;
    }
    cout << ans << endl;

    return 0;
}

Viral Advertising C Sharp Solution

using System;
using System.Collections.Generic;
using System.IO;
class Solution {
    static void Main(String[] args) {
        /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution */
        int n = int.Parse(Console.ReadLine());
        int m = 5/2;
        int sum = m;
        for(int i=1;i<n;i++)
            {
            m = m*3/2;
            sum+=m;
        }
        Console.WriteLine(sum);
    }
}

Viral Advertising Java Solution

import java.io.*;
import java.math.*;
import java.security.*;
import java.text.*;
import java.util.*;
import java.util.concurrent.*;
import java.util.function.*;
import java.util.regex.*;
import java.util.stream.*;
import static java.util.stream.Collectors.joining;
import static java.util.stream.Collectors.toList;

class Result {

    /*
     * Complete the 'viralAdvertising' function below.
     *
     * The function is expected to return an INTEGER.
     * The function accepts INTEGER n as parameter.
     */

    public static int viralAdvertising(int n) {
    // Write your code here
        int cummulative = 2;
        int shared = 5;
        int liked = 2;
        int day = 1;
        
        while (day < n) {
            shared = Math.floorDiv(shared,2) * 3;
            liked = Math.floorDiv(shared,2);
            cummulative += liked;
            day++;
        }
        return cummulative;
    }

}

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

        int n = Integer.parseInt(bufferedReader.readLine().trim());

        int result = Result.viralAdvertising(n);

        bufferedWriter.write(String.valueOf(result));
        bufferedWriter.newLine();

        bufferedReader.close();
        bufferedWriter.close();
    }
}

Viral Advertising Javascript Solution

function processData(input) {
    const n = Number(input);
    let people = 5;
    let result = 0;
    for(var i=0; i<n; i++) {
        result += Math.floor(people / 2);
        people = Math.floor(people / 2) * 3;
    }
    console.log(result);
} 

process.stdin.resume();
process.stdin.setEncoding("ascii");
_input = "";
process.stdin.on("data", function (input) {
    _input += input;
});

process.stdin.on("end", function () {
   processData(_input);
});

Viral Advertising Python Solution

n = int(input().strip())
people = 5
soma = 0

for i in range(n):
    people //= 2
    soma += people
    people *= 3

print(soma)