[LeetCode] 535. Encode and Decode TinyURL 编码和解码短网址

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.

Python:

class Codec:
    def __init__(self):
        self.__random_length = 6
        self.__tiny_url = "http://tinyurl.com/"
        self.__alphabet = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
        self.__lookup = {}

    def encode(self, longUrl):
        """Encodes a URL to a shortened URL.
        
        :type longUrl: str
        :rtype: str
        """
        def getRand():
            rand = []
            for _ in xrange(self.__random_length):
                rand += self.__alphabet[random.randint(0, len(self.__alphabet)-1)]
            return "".join(rand)
        
        key = getRand()
        while key in self.__lookup:
            key = getRand()
        self.__lookup[key] = longUrl
        return self.__tiny_url + key

    def decode(self, shortUrl):
        """Decodes a shortened URL to its original URL.
        
        :type shortUrl: str
        :rtype: str
        """
        return self.__lookup[shortUrl[len(self.__tiny_url):]]

 Python：Using sha256

from hashlib import sha256

class Codec:

    def __init__(self):
        self._cache = {}
        self.url = 'http://tinyurl.com/'

    def encode(self, long_url):
        """Encodes a URL to a shortened URL.
        :type long_url: str
        :rtype: str
        """
        key = sha256(long_url.encode()).hexdigest()[:6]
        self._cache[key] = long_url
        return self.url + key

    def decode(self, short_url):
        """Decodes a shortened URL to its original URL.
        :type short_url: str
        :rtype: str
        """
        key = short_url.replace(self.url, '')
        return self._cache[key]

C++:

class Solution {
public:
    Solution() : gen_((random_device())()) {
    }

    // Encodes a URL to a shortened URL.
    string encode(string longUrl) {
        string key = getRand();
        while (lookup_.count(key)) {
            key = getRand();
        }
        lookup_[key] = longUrl;
        return "http://tinyurl.com/" + key;
    }

    // Decodes a shortened URL to its original URL.
    string decode(string shortUrl) {
        return lookup_[shortUrl.substr(tiny_url.length())];
    }

private:
    string getRand() {
        string random;
        for (int i = 0; i < random_length; ++i) {
            random += alphabet_[uniform_int_distribution<int>{0, alphabet_.length() - 1}(gen_)];
        }
        return random;
    }

    const int random_length = 6;
    const string tiny_url = "http://tinyurl.com/";
    const string alphabet_ = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
    default_random_engine gen_;
    unordered_map<string, string> lookup_;
};

　　

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[LeetCode] 534. Design TinyURL 设计短网址

 

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