Mars Exploration in Algorithm | HackerRank Programming Solutions | HackerRank Problem Solving Solutions in Java [💯Correct]

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In this post, you will find the solution for Mars Exploration in Java-HackerRank Problem. We are providing the correct and tested solutions of coding problems present on HackerRank. If you are not able to solve any problem, then you can take help from our Blog/website.

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Introduction To Algorithm

The word Algorithm means “a process or set of rules to be followed in calculations or other problem-solving operations”. Therefore Algorithm refers to a set of rules/instructions that step-by-step define how a work is to be executed upon in order to get the expected results. 

Advantages of Algorithms:

  • It is easy to understand.
  • Algorithm is a step-wise representation of a solution to a given problem.
  • In Algorithm the problem is broken down into smaller pieces or steps hence, it is easier for the programmer to convert it into an actual program.

Link for the ProblemMars Exploration – Hacker Rank Solution

Mars Exploration – Hacker Rank Solution


A space explorer’s ship crashed on Mars! They send a series of SOS messages to Earth for help.

1453204202 9e3fd295bb NASA Mars Rover

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


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


  • int: the number of letters changed during transmission

Input Format

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


  •  will contain only uppercase English letters, ascii[A-Z].

Sample Input 0


Sample Output 0


Explanation 0

 = SOSSPSSQSSOR, and signal length . They sent  SOS messages (i.e.: ).

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

Sample Input 1


Sample Output 1


Explanation 1

 = SOSSOT, and signal length . They sent  SOS messages (i.e.: ).

Expected Signal: SOSSOS     
Received Signal: SOSSOT
Difference:           X

Sample Input 2


Sample Output 2


Explanation 2

Since no character is altered, return 0.

Mars Exploration – Hacker Rank Solution
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;
public class Solution {
    public static void main(String[] args) {
        Scanner in = new Scanner(;
        String S =;
        int numChanged = 0;
        for(int i = 0; i < S.length(); i++)
            if(i % 3 == 1)
                if(S.charAt(i) != 'O')
                if(S.charAt(i) != 'S')

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