Too Long; Didn't Read
Leetcode.com is a website where people–mostly software engineers–practice their coding skills. It’s pretty similar to sites like HackerRank & Topcoder which will rank your code written for a particular problem against the ones submitted by other users. The most fundamental thing to do before writing code is first to understand the algorithms and various techniques. Don't run too fast and don’t run into solving the problems without getting a proper understanding of the underlying data structures like a linked list, stack, queue, tree.