C++     Design     Hash Function     Hash Table     Medium     String    

Problem Statement:

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.

Solution:

 
class Solution {
public:
    unordered_map<int,string> int2url;
    unordered_map<string,int> url2int;
    string base_url = "http://tiny.io/";
    // Encodes a URL to a shortened URL.
    string encode(string longUrl) {
        if (url2int.find(longUrl)==url2int.end())
        {
            int ctr=url2int.size();
            url2int[longUrl] = ctr;
            int2url[ctr] = longUrl;
        }
        return base_url+to_string(url2int[longUrl]);
    }

    // Decodes a shortened URL to its original URL.
    string decode(string shortUrl) {
        string nstr = string(shortUrl.begin()+15,shortUrl.end());
        int n = stoi(nstr);
        return int2url[n];
    }
};