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

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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.

• 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`

### Problem:

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, , determine how many letters of the `SOS` message have been changed by radiation.

Example

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, .

Constraints

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

Sample Input 0

```SOSSPSSQSSOR
```

Sample Output 0

```3
```

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

```SOSSOT
```

Sample Output 1

```1
```

Explanation 1

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

```Expected Signal: SOSSOS
Difference:           X
```

Sample Input 2

```SOSSOSSOS
```

Sample Output 2

```0
```

Explanation 2

Since no character is altered, return 0.

`Mars Exploration – Hacker Rank Solution`
```import java.io.*;
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(System.in);
String S = in.next();
int numChanged = 0;

for(int i = 0; i < S.length(); i++)
{
if(i % 3 == 1)
{
if(S.charAt(i) != 'O')
{
numChanged++;
}
}
else
{
if(S.charAt(i) != 'S')
{
numChanged++;
}
}
}

System.out.println(numChanged);
}```  