Note: This is a companion problem to the System Design problem: Design TinyURL.
TinyURL is a URL shortening service where you enter a URL such as https://leetcode.com/problems/design-tinyurl
and it returns a short URL such as http://tinyurl.com/4e9iAk.
Design the encode and decode methods for the TinyURL service. There
is no restriction on how your encode/decode algorithm should work. You just need to ensure
that a URL can be encoded to a tiny URL and the tiny URL can be decoded to the original URL.