# Mars Exploration Hacker Rank Solution Best & Easiest

Mars Exploration Problem Solution

In this post, we will solve Mars Exploration HackerRank Solution. This problem (Mars Exploration) is a part of HackerRank Problem Solving series.

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.

## Constraints

• 1 <= length of s <= 99
• length of s modulo 3 = 0
• s will contain only uppercase English letters, ascii[A-Z].

Sample Input 0

``SOSSPSSQSSOR``

Sample Output 0

``3``

Explanation 0

s = 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

``1``

Explanation 1

s = SOSSOT, and signal length |s| = 6. They sent 2 `SOS` messages (i.e.: 6/3 = 2).

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

Sample Input 2

``SOSSOSSOS``

Sample Output 2

``0``

Explanation 2

Since no character is altered, return 0.

## Counting Valleys Hacker Rank Solution

### Problem solution in Python programming:

```def marsExploration(s):
l,st,flag,count = len(s)-1,"sos",0,0
while(l>=0):
if flag == 3:
flag = 0
if st[flag] != s[l].lower():
count += 1
flag += 1
l -= 1
return(count)
```

### Problem solution in C++ programming:

```public static int marsExploration(String s) {

int sum = 0;
int i = 0;

while(i<s.length()){
if(s.charAt(i) != 'S'){
sum++;
}
if(s.charAt(i+1) != 'O'){
sum++;
}
if(s.charAt(i+2) != 'S'){
sum++;
}
i+=3;
}

return sum;
}
```

### Problem solution in JavaScript programming:

```function marsExploration(s) {
let mess = 'SOS', expected_mess = '';
let len = s.length  / 3, count = 0;
// To create Expected message
while(len--) {
expected_mess+=mess;
}
for(let i=0; i<expected_mess.length; i++){
if(s[i] !== expected_mess[i])
count++;
}
return count

}
```