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535. Encode and Decode TinyURL

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Description

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 a class to encode a URL and decode a tiny URL.

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.

Implement the Solution class:

• Solution() Initializes the object of the system.
• String encode(String longUrl) Returns a tiny URL for the given longUrl.
• String decode(String shortUrl) Returns the original long URL for the given shortUrl. It is guaranteed that the given shortUrl was encoded by the same object.

 

Example 1:

Input: url = "https://leetcode.com/problems/design-tinyurl"
Output: "https://leetcode.com/problems/design-tinyurl"

Explanation:
Solution obj = new Solution();
string tiny = obj.encode(url); // returns the encoded tiny url.
string ans = obj.decode(tiny); // returns the original url after deconding it.

 

Constraints:

• 1 <= url.length <= 104
• url is guranteed to be a valid URL.

Solutions

Python3

class Codec:
    def __init__(self):
        self.code_url = {}
        self.count = 0
        self.prefix_url = 'http://tinyurl.com/'

    def encode(self, longUrl: str) -> str:
        """Encodes a URL to a shortened URL.
        """
        self.count += 1
        code = str(hex(self.count))[2:]
        self.code_url[code] = longUrl
        return self.prefix_url + code

    def decode(self, shortUrl: str) -> str:
        """Decodes a shortened URL to its original URL.
        """
        code = shortUrl.replace(self.prefix_url, '')
        return self.code_url[code]

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

Java

public class Codec {
    private Map<String, String> code2Url = new HashMap<>();
    private int count = 0;
    private static final String prefixUrl = "http://tinyurl.com/";

    // Encodes a URL to a shortened URL.
    public String encode(String longUrl) {
        String code = Integer.toHexString(++count);
        code2Url.put(code, longUrl);
        return prefixUrl + code;
    }

    // Decodes a shortened URL to its original URL.
    public String decode(String shortUrl) {
        String code = shortUrl.replace(prefixUrl, "");
        return code2Url.get(code);
    }
}

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

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