HackerRank Mars Exploration Problem Solution

In this post, we will solve HackerRank Mars Exploration Problem Solution. A space explorer’s ship crashed on Mars! They send a series of SOS messages to Earth for help.

Letters in some of the SOS messages are altered by cosmic radiation during transmission. Given the signal received by Earth as a string, s, determine how many letters of the SOS message have been changed by radiation.

Example

s = SOSTOT

The original message was SOSSOS. Two of the message’s characters were changed in transit.

Function Description

Complete the marsExploration function in the editor below.

marsExploration has the following parameter(s):

string s: the string as received on Earth

Returns

int: the number of letters changed during transmission

Input Format

There is one line of input: a single string, s.

Sample Input 0

SOSSPSSQSSOR

Sample Output 0

Explanation 0
8 = SOSSPSSQSSOR, and signal length |s|= 12. They sent 4 sos messages (i.e.: 12/3 = 4).

Expected signal: SOSSOSSOSSOS
Recieved signal: SOSSPSSQSSOR
Difference:          X  X   X

Sample Input 1

SOSSOT

Sample Output 1

Explanation 1
S = SOSSOT, and signal length |s = 6. They sent 2 sos messages (i.e.: 6/3 = 2).

Sample Input 2

SOSSOSSOS

Sample Output 2

Explanation 2

Since no character is altered, return 0.

HackerRank Mars Exploration Problem Solution

Mars Exploration C Solution

#include <math.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <assert.h>
#include <limits.h>
#include <stdbool.h>

int main(){
    int p, n;
    char* S = (char *)malloc(10240 * sizeof(char));
    scanf("%s",S);
    
    n = p = 0;
    while (S[p] != '\0')
    {
        if (S[p++] != 'S') n++;
        if (S[p++] != 'O') n++;
        if (S[p++] != 'S') n++;        
    }
    
    printf ("%d\n", n);
    
    return 0;
}

Mars Exploration C++ 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 */   
  
  auto f = [&](const std::string& s){
    int cnt = 0;
    std::string sos("SOS");
    for(size_t i = 0; i < s.length(); ++i){
      if(s[i] != sos[i%3]) cnt++;
    }
    return cnt;
  };
  
  std::string s;
  std::cin >> s;
  std::cout << f(s) << std::endl;
  return 0;
}

Mars Exploration C Sharp Solution

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
class Solution {

    static void Main(String[] args) {
        string S = Console.ReadLine();
        
        string t = "";
        int count = 0;
        
        for(int i = 0; i < S.Length; i+=3){
            
            t = S.Substring(i,3);
            
            if(t.Substring(0,1) != "S"){
                count ++;
                
            }
            if(t.Substring(1,1) != "O"){
                count ++;
                
            }
            if(t.Substring(2,1) != "S"){
                count ++;
                
            }
            
        }
        
        Console.WriteLine(count);
        
        
    }
}

Mars Exploration 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 'marsExploration' function below.
     *
     * The function is expected to return an INTEGER.
     * The function accepts STRING s as parameter.
     */

    public static int marsExploration(String s) {
        int count = 0;
        for(int i = 0;i<s.length()-2;i+=3) {
            if(!s.substring(i, i+1).equals("S")) {
                count++;
            }
            if(!s.substring(i+1, i+2).equals("O")) {
                count++;
            }
            if(!s.substring(i+2, i+3).equals("S")) {
                count++;
            }
        }
        return count;
    }

}

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")));

        String s = bufferedReader.readLine();

        int result = Result.marsExploration(s);

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

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

Mars Exploration JavaScript Solution

process.stdin.resume();
process.stdin.setEncoding('ascii');

var input_stdin = "";
var input_stdin_array = "";
var input_currentline = 0;

process.stdin.on('data', function (data) {
    input_stdin += data;
});

process.stdin.on('end', function () {
    input_stdin_array = input_stdin.split("\n");
    main();    
});

function readLine() {
    return input_stdin_array[input_currentline++];
}

/////////////// ignore above this line ////////////////////

function main() {
    var s = readLine();
    console.log(unexpectedLetters(s));
}

function unexpectedLetters(s) {
    var expected = 0;
    for (var i = 0; i < s.length; i+= 3) {
        expected += boolToInt(s[i] === 'S') +
                    boolToInt(s[i + 1] === 'O') + 
                    boolToInt(s[i + 2] === 'S');
    }
    return s.length - expected;
}

function boolToInt(expr) {
    return expr ? 1 : 0;
}

Mars Exploration Python Solution

#!/bin/python3

import sys


S = input().strip()

count = 0
for i in range(len(S)):
    if i % 3 == 0 or i % 3 == 2:
        if S[i] != 'S':
            count += 1
    elif i % 3 == 1 and S[i] != 'O':
        count += 1
print(count)