不好的方法:

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public class Codec {

    List<String> urls = new ArrayList<>();
    
    // 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);
    }
}

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

Good:

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class Codec:
     
    def __init__(self):
        self.pool = itertools.permutations(string.printable, 6)
        self.cache = {}
     
    def encode(self, longUrl):
        key = next(self.pool)
        self.cache[key] = longUrl
        return key
         
    def decode(self, shortUrl):
        key = shortUrl
        return self.cache[key]