added best time to buy sell stock IV in leetcode folder

[dhruvin5]

Related Issue

• Info about the related issue Provided solution of the problem Best time to buy and sell stock IV[Hard] of leetcode Closes: #515

Describe the changes you've made

C++ solution (with commented explanations) of leetcode problem Best time to buy and sell stock IV[Hard] 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)

NA

Checklist:

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

• [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, particularly whereever it was hard to understand.
• [x] My changes generate no new warnings.

Additional Info (optional)

Any additional information you want to give

[dhruvin5]

Can you please check this @kanak22