This C++ program takes an integer e and a string input, then applies a simple encryption algorithm to each digit in the input string by adding e to it and taking the result modulo 10. Here's the program rewritten with comments to explain each part:

include

using namespace std;

int main() { int e; // Declare an integer variable e to store the encryption key string input; // Declare a string variable input to store the input string

// Prompt the user to enter the input string followed by the encryption key
cout << "Enter the input string: ";
cin >> input;
cout << "Enter the encryption key: ";
cin >> e;

// Loop through each character of the input string
for (int i = 0; i < input.length(); ++i) {
    // Encrypt the current digit by adding e and taking modulo 10
    // Note: The expression 'input[i] - '0'' converts the character digit to its integer equivalent
    // Then add the encryption key e and take modulo 10 to ensure the result is a single digit
    // Finally, convert the result back to string and output it
    cout << to_string((input[i] - '0' + e) % 10);
}

// Output a newline character for better formatting
cout << endl;

return 0;

}

The first step you should take is to examine the code for any errors that may be causing problems during execution. Additionally, please visit the following page to review the code's syntax, as this will help you gain a better understanding of security key spaces.

First thing you should be check out the what are errors occurs in that code which creating problem when you trying to execute it. Also visit this page and check out the cyntex of the code, then you actualy understand security key spaces.

Short C++ solution

#include <iostream>
using namespace std;


int main() {
    int e;
    string input;
    cin >> input >> e;
    for (int i=0; i < input.length(); ++i)
        cout << to_string((input[i] - '0' + e) % 10);
    return 0;
}

php solution with function for reuse...

<?php
declare(strict_types = 1);

$_fp = fopen("php://stdin", "r");
echo f(fgets($_fp), (int)fgets($_fp));

function f(string $x, int $e): string
{
    for($i=strlen($x)-1; $i--;)
        $x[$i] = ($x[$i] + $e) % 10;
    return $x;
}

?>