Add solutions to leetcode problems.

[rathoresrikant]

Add the solutions in Leetcode folder with proper names.

[varunkmr19]

I've added solutions for three problems on Leetcode. Check the pr #176

[3ZadeSSG]

I have added three problems on Leetcode. Check PR #225 (It contains two commits, one for Hackerrank and other for Leetcode). Also link to problems have been given in code as a comment.

[rohan2734]

where are the questions to add the solution , i can find the file but what to do? as if, please mention the quesiton. so that we can give solution.