Question Definition
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.
Java Solution
public class Codec {
HashMap<String, String> hashToUrl = new HashMap<String, String>();
HashMap<String, String> urlToHash = new HashMap<String, String>();
String tinyUrlBase = "http://tinyurl.com/";
String characters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
Random random = new Random();
// Encodes a URL to a shortened URL.
public String encode(String longUrl) {
if (urlToHash.containsKey(longUrl))
return tinyUrlBase + urlToHash.get(longUrl);
StringBuilder hash = new StringBuilder();
do {
for (int i=0; i<6; i++) {
hash.append(characters.charAt(random.nextInt(characters.length())));
}
} while (hashToUrl.containsKey(hash.toString()));
hashToUrl.put(hash.toString(), longUrl);
urlToHash.put(longUrl, hash.toString());
return tinyUrlBase + hash.toString();
}
// Decodes a shortened URL to its original URL.
public String decode(String shortUrl) {
return hashToUrl.get(shortUrl.substring(tinyUrlBase.length()));
}
}
// Your Codec object will be instantiated and called as such:
// Codec codec = new Codec();
// codec.decode(codec.encode(url));
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