535. Encode and Decode TinyURL

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 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.

Constraints

Approach

Links

• GeeksforGeeks

• Leetcode

• ProgramCreek

• YouTube

Examples

Example 1

Solutions

Solution 1

/**
 * Time complexity : 
 * Space complexity : 
 */

public class Codec {
    
    private Map<String, String> longShortMap = new HashMap();
    private Map<String, String> shortLongMap = new HashMap();
    private final String TINY_URL = "http://tinyurl.com/";
    private int id = 0;
    private String code = "abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";

    // Encodes a URL to a shortened URL.
    public String encode(String longUrl) {
        if(longShortMap.containsKey(longUrl)) {
            return longShortMap.get(longUrl);
        }
        StringBuilder shortUrl = new StringBuilder();
        int currId = id;
        for(int i = 0; i < 6; i++) {
            int codeIndex = currId % 62;
            currId /= 62;
            shortUrl.append(code.charAt(codeIndex));
        }
        longShortMap.put(longUrl, shortUrl.toString());
        shortLongMap.put(shortUrl.toString(), longUrl);
        id++;
        return TINY_URL + shortUrl.toString();
    }

    // Decodes a shortened URL to its original URL.
    public String decode(String shortUrl) {
        return shortLongMap.get(shortUrl.replace(TINY_URL, ""));
    }
}

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

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