535. Encode and Decode TinyURL

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.

https://leetcode.com/problems/encode-and-decode-tinyurl/solution/



Simply put, hashCode() returns an integer value, generated by a hashing algorithm.




// accepted 
public class Codec {
    // example of a long url : 
    // https://www.google.com/search?q=long+url&num=100&rlz=1C5CHFA_enUS766US767&source=lnms&tbm=isch&sa=X&ved=0ahUKEwj4vMD-yazeAhWDAHwKHdlOCuwQ_AUIDigB&biw=1343&bih=734
    
    // hashed = hashcode(long url) = 4e9iAk
    // example of a short url : 
    // "http://tinyurl.com/4e9iAk"
    // map < key : hashedcode , value : long url > 
    
    // process : we get a long url, we get the hashcode of this long url, we store the hashed result and the long url to the 
    // map, 
    // return http://tinyurl.com/ + hashed result 
    
    // for decoding : 
    // we have the short url, we get the hashsed result part, and then we return the long url from the map
    
    Map<Integer, String> map = new HashMap<>();
    // Encodes a URL to a shortened URL.
    public String encode(String longUrl) {
        Integer hashResult = longUrl.hashCode();
        map.put(hashResult, longUrl);
        return "http://tinyurl.com/" + hashResult; // string concatenation with an integer ? yes 
        
    }

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