Upload 2Sum problem from leetcode into online_challenges sub repo

[amansheoran15]

This is a(n):

• New algorithm
• Update to an existing algorithm
• Error
• Proposal to the Repository

Details:
Link to the problem : https://leetcode.com/problems/two-sum/

I want to add solution to this problem in online_challenges/leetcode sub repo.

[TheNourhan]

can i do that please?

[JatinMGulati]

Hello I would like to this project as well providing good quality code and make sure the task is completed very quickly please assign this project to me.