Leetcode 535 - Encode and Decode TinyURL

Note:

  • Learned how to use random().toString(36) to generate random strings.
  • 36-base system use all 0-9, a-z, A-Z, which is quite useful.

Question:

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:

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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.

Code:

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/**
* Encodes a URL to a shortened URL.
*
* @param {string} longUrl
* @return {string}
*/
let map = new Map();
var encode = function(longUrl) {
let hash;
while (hash === undefined || map.has(hash)) {
hash = Math.random().toString(36).slice(0, 10);
}
map.set(hash, longUrl);
return 'http://tinyurl.com/' + hash;
};

/**
* Decodes a shortened URL to its original URL.
*
* @param {string} shortUrl
* @return {string}
*/
var decode = function(shortUrl) {
return map.get(shortUrl.slice(19));
};

/**
* Your functions will be called as such:
* decode(encode(url));
*/