Question

Write a C++ program which performs a rot 13 substitution. Must be in C++. Thank you.

Answer 1

CodeToCopy:

rot13.cpp

#include <iostream> /* for cin, cout */

using namespace std;

/* string variable holds lower case letters */

string lower_case_letters = "abcdefghijklmnopqrstuvwxyz";

/* string variable holds upper case letters */

string upper_case_letters = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

/* function encodes and decodes the input string using

* rot13 substitution cipher */

string rot13(string input) {

   

    /* string variable to hold output */

    string output;

   

    /* holds the position of input character in alphabet */

    int letter_pos;

   

    /* loop to iterate over input string */

    for (int i = 0; i < input.size(); ++i) {

       

        /* finding the position of input character in lower_case_alphabet */

        letter_pos = lower_case_letters.find(input[i]);

        if (letter_pos < 0) {

           

             /* finding the position of input character in upper_case_alphabet */

            letter_pos = upper_case_letters.find(input[i]);

           

            if (letter_pos < 0) {

                /* its not a character in alphabet, so not doing anything */       

                output.append(1, input[i]);

                continue;

            }

           

            /* getting the position of 13th character from current character */

            letter_pos = (letter_pos + 13) % 26;

           

            /* appending it to output */

            output.append(1, upper_case_letters[letter_pos]);           

        }

       

        else {

            /* getting the position of 13th character from current character */

            letter_pos = (letter_pos + 13) % 26;

           

            /* appending it to output */

            output.append(1, lower_case_letters[letter_pos]);

        }

  }

   

    /* returning input */

    return output;

}

/* driver code to test to above function */

int main() {

   

    /* taking input from the user */

    string input;

    cout << "input: ";

    cin >> input;

   

    /* getting rot13 encoded text and printing */

    string output = rot13(input);

   

    cout << "encoded: " << output << endl;

   

    /* getting rot13 decoded text and printing */

    cout << "decoded: " << rot13(output) << endl;

   

   

    return 0;

}

OutputScreenshot: