Related Issue

• Info about the related issue
  Provided solution of the problem cheapest flight within k stops[Medium] of leetcode
  Closes: Cheapest flight within k stops(graphs) #518

Describe the changes you've made

C++ solution (with commented explanations) of leetcode problem cheapest flight within k stops[Medium]
I have created a folder in the leetcode folder with the same name as that of the problem
I have attached the c++ file inside the folder

Mention any unusual behaviour of your code (Write NA if not)

Any unusual behaviour of your code

Checklist:

(To mark, write x inside the square brackets like this: [x])

• My code follows the guidelines of this project.
• I have performed a self-review of my own code.
• I have commented my code, particularly whereever it was hard to understand.
• My changes generate no new warnings.

Additional Info (optional)

Any additional information you want to give