I'm needing help with the following c++ code:

Create a program that decodes and encodes plain text using a simple Caesar cipher. Text is encoded using a Caesar cipher by simple substitution wherein the letters in the message are replaced with some letter of a fixed number down the alphabet. You will use the header file so that you can access a method (library function) named .at(position). This method will return the character that is found at a particular index position which is passed to the method. (Hint: remember that char can be type cast as int which would allow you to manipulate the ASCII value of the char)

The main function should have a menu with two options: decode or encode. Those options should call separate functions decode and encode. Encode function receives a string that is normal text and returns an encoded string. The Decode function should receive the coded string and return 25 different lines, each with a possible solution to the message. Those lines are created by showing each possibility, shifting the letters down the alphabet by one each time.

Here is what I have completed:

#include

#include

#include

#include

/*

Name: John Hawkins

Date: 3/24/2018

File Name: HawkinsJ Caesar Cypher

Description: This program allows the user to encrypt and decrypt messages using teh Caesar Cypher.

*/

using namespace std;

void encode();

//encodes a string message from teh user and outputs the encoded message

void decode();

//prompts the user for an encoded message and displays all possible (25)

//decoded plain text

int main(int argc, char** argv)

{

string strChoice;

do

{

cout<< "++++++++++Caesar Cypher++++++++++++ "

<< "1. \tEncode "

<< "2. \tDecode "

<< "select a menu option: ";

//read user choice

getline(cin,strChoice);

if(strChoice == "1")

{

encode();

}

else if(strChoice == "2")

{

//decode();

}

else

{

cout<< "Invalid choice. choose 1 or 2";

}

}while(strChoice != "1" || strChoice != "2");

return 0;

}

void encode()

{

//variables

string strMessage;

srand(time(0));

int randNum = rand()%25+1;

char c;

//prompt user for the message

cout<< "Type a message to enode: ";

getline(cin,strMessage);

for(int n=0; n< strMessage.length(); n++)

{

//weed out spaces

if(isalpha(strMessage.at(n)))

{

c = toupper(strMessage.at(n));

c = (((c-65)+randNum)%26)+65;

}

else

{

c = strMessage.at(n);

}

cout<< c;

}

cout<< endl << endl;

}//end encode