[daily training] 535 Encryption and decryption of tinyurl

subject

TinyURL It's a kind of URL Simplify services , such as ： When you enter a URL https://leetcode.com/problems/design-tinyurl when , It will return a simplified URL http://tinyurl.com/4e9iAk . Please design a class to encrypt and decrypt TinyURL .

There is no limit to how encryption and decryption algorithms are designed and operated , You just need to guarantee one URL Can be encrypted into a TinyURL , And this TinyURL It can be restored to the original by decryption URL .

Realization Solution class ：

Solution() initialization TinyURL System object .
String encode(String longUrl) return longUrl Corresponding TinyURL .
String decode(String shortUrl) return shortUrl The original URL . The subject data guarantees a given shortUrl Is encrypted by the same system object .

Example ：
Input ：url = “https://leetcode.com/problems/design-tinyurl”
Output ：“https://leetcode.com/problems/design-tinyurl”
explain ：
Solution obj = new Solution();
string tiny = obj.encode(url); // Returns the result of encryption TinyURL .
string ans = obj.decode(tiny); // Returns the original after decryption URL .

Tips ：
1 <= url.length <= 10⁴
Topic data assurance url Is an effective URL

Code

package dayLeetCode;

import java.util.HashMap;
import java.util.Map;

public class dayleetcode535 {
    
    //  Add a unique ID 
    Map<Integer, String> map = new HashMap<>();
    int id;

    // Encodes a URL to a shortened URL.
    public String encode(String longUrl) {
    
        id++;
        map.put(id, longUrl);
        return "http://tinyurl.com/" + id;

    }

    // Decodes a shortened URL to its original URL.
    public String decode(String shortUrl) {
    
        //  obtain id It's the number one character 
        int k = shortUrl.lastIndexOf('/') + 1;
        //  Before removal k Characters 
        int id = Integer.parseInt(shortUrl.substring(k));

        return map.get(id);

    }
}