Added deMux calculator

[Rishika631]

Issue Id you have worked upon -

386

Briefly explain your program logic -

For deMux calculator I first find the output line which will be selected using the input string that is by converting it into decimal value and then find the binary string on that particular selected output string whose length should not exceed n.

Screenshots(Attach 2 screenshots of your own input and output) -

By raising this PR I affirm that -

• [x] My code follows the guidelines of this project.
  

• [x] I have performed a self-review of my own code.
  

• [x] I have commented my code.
  

• [x] My code gives the correct output.
  

• [x] I affirm that I strictly follow contributing guidelines and code of conduct.

[SarthakKeshari]

Congratulations 🎉 @Rishika631 on your contribution. Thanks for adding value to this repository. 😊

Let's celebrate this fest 😃 by providing more developers 👨‍💻👩‍💻 an opportunity to contribute. Help us make this repository reach far and more by sharing this to your friends and colleagues.

Your efforts can make difference.

[SarthakKeshari]

Hey 👋, may you also encourage us by clicking the star icon on the repository main page. ⭐

[Rishika631]

Thank you! I will definitely share it with my friends.