535. Encode and Decode TinyURL

https://leetcode.com/problems/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.

---

	public class Codec {
	Map<String, String> map = new HashMap<String, String>();
	Map<String, String> invMap = new HashMap<String, String>();
	String HOST ="http://tinyurl.com/";
	String keys = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
	// Encodes a URL to a shortened URL.
	public String encode(String longUrl) {
	if (map.containsKey(longUrl)) {
	return map.get(longUrl);
	}
	String key = "";
	do {
	StringBuilder sb = new StringBuilder();
	for (int i = 0; i < 6; i++) {
	sb.append(keys.charAt((int)Math.random() * keys.length()));
	}
	key = sb.toString();
	} while (map.containsKey(key));
	key = HOST + key;
	map.put(longUrl, key);
	invMap.put(key, longUrl);
	return key;
	}
	// Decodes a shortened URL to its original URL.
	public String decode(String shortUrl) {
	return invMap.get(shortUrl);
	}
	}
	// Your Codec object will be instantiated and called as such:
	// Codec codec = new Codec();
	// codec.decode(codec.encode(url));

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