【Leetcode】535. Encode and Decode TinyURL

Question：

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.

Tips：

将长的url转换为短url 将短url转换为长的url。长url与短url之间有一个映射，保证一致。
如输入https://leetcode.com/problems/design-tinyurl 编码之后返回http://tinyurl.com/4e9iAk
输入http://tinyurl.com/4e9iAk，decode之后也要返回https://leetcode.com/problems/design-tinyurl。

编码方式没有限制，主要是code与decode之后 结果要相同。

思路：

code:

输入类似：https://leetcode.com/problems/design-tinyurl

用longUrl的哈希值作为hashmap的key，longUrl作为value，组成键值对，保存在map中。

返回"http://tinyurl.com/"+longUrl的哈希值，即键值。

decode：

输入类似：http://tinyurl.com/4e9iAk

根据http://tinyurl.com/ 后面的4e9iAk作为key 来查找对应的value就是longUrl

代码：（使用hashmap）

package medium;

import java.util.HashMap;
import java.util.Map;

public class L535EncodeAndDecodeTinyURL {
    //即将长的url转换为短url 将短url转换为长的url。
    //长url与短url之间有一个映射，保证一致。
    //如输入https://leetcode.com/problems/design-tinyurl 编码之后返回http://tinyurl.com/4e9iAk
    //输入http://tinyurl.com/4e9iAk，decode之后也要返回https://leetcode.com/problems/design-tinyurl
    Map<Integer, String> map = new HashMap<>();

    // Encodes a URL to a shortened URL.
    public String encode(String longUrl) {
        map.put(longUrl.hashCode(), longUrl);
        //System.out.println("long hashCode"+longUrl.hashCode());
        return "http://tinyurl.com/" + longUrl.hashCode();
    }

    // Decodes a shortened URL to its original URL.
    public String decode(String shortUrl) {
        return map.get(Integer.parseInt(shortUrl.replace("http://tinyurl.com/", "")));
    }

    // Your Codec object will be instantiated and called as such:
    public static void main(String[] args) {
        L535EncodeAndDecodeTinyURL l535 = new L535EncodeAndDecodeTinyURL();
        System.out.println(l535.decode(l535.encode("https://leetcode.com/problems/design-tinyurl")));
    }
}