535. Encode and Decode TinyURL

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.

题目中说了他的测试实例是：

// Your Codec object will be instantiated and called as such:
// Codec codec = new Codec();
// codec.decode(codec.encode(url));

所以出现了下面的joke版答案，还ac了：

public class Codec {    // Encodes a URL to a shortened URL.    public String encode(String longUrl) {        return longUrl;    }    // Decodes a shortened URL to its original URL.    public String decode(String shortUrl) {        return shortUrl;    }}// Your Codec object will be instantiated and called as such:// Codec codec = new Codec();// codec.decode(codec.encode(url));

相对正规的解法代码如下：

public class Codec {    List<String> urls = new ArrayList<String>();        // Encodes a URL to a shortened URL.    public String encode(String longUrl) {        urls.add(longUrl);        return String.valueOf(urls.size() - 1);    }    // Decodes a shortened URL to its original URL.    public String decode(String shortUrl) {        int index = Integer.parseInt(shortUrl);        return urls.get(index);    }}