Largest Number at least twice of others.cpp

[paridhi-jain-047]

I want to add source code of this problem statement taken from leetcode.

Here is the link of it:- https://leetcode.com/problems/largest-number-at-least-twice-of-others/

This is my pull request ID #481

If you find it useful and purely plagiarism free. Then please merge it on your code base repository.

[vivekarora-02]

Hey there, I would like to contribute to this issue. Can you please assign me this issue?
ThankYou!.

[shashwat010]

Please assing me this issue. I would be making my first contribution in open-source.