Why this getline function is not working in code?

Question

I was making a code of vigenere cryptography and this getline function is not working.
Copy the code into your IDE then try.
I am using Codeblock.
https://code.sololearn.com/cZmdbO8R381L/?ref=app

Answer 1

Can you give me sample string for <key> and <message> for testing? also the expected result string?

As I see it, you mix up C and C++ here, looking at how you measure the length of <key> for example. But I see you already know C++ string has `length` method which does the job.

Answer 2

The call to std::getline() will result in an empty string because the newline character from your prior input is still in the input buffer. std::getline() will encounter that newline character, causing it to stop immediately after extracting and discarding the newline character because it acts as a delimiter.
You can discard such leading whitespace characters with a call to std::ws:

https://en.cppreference.com/w/cpp/io/manip/ws

Just change
std::getline( std::cin, message );
to
std::getline( std::cin >> std::ws, message);
and you should be fine. I didn't look for any other errors right now, but this should get you started.