535.Encode and Decode TinyURL

Posted on | In

Solution 1: accepted 7ms

Increment and simply mapping the index. 

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
public class Codec {
    
    private static HashMap<String, String> stl = new HashMap<>();
    private static HashMap<String, String> lts = new HashMap<>();
    private final String BASE_URL = "http://tinyurl.com/";
    private static char[] dic = {'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z','a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};
    
    // Encodes a URL to a shortened URL.
    public String encode(String longUrl) {
        int size = stl.size();
        String tiny = getTiny(size);
        stl.put(tiny, longUrl);
        lts.put(longUrl, tiny);
        return BASE_URL + tiny;
    }
    // Decodes a shortened URL to its original URL.
    public String decode(String shortUrl) {
        String tiny = shortUrl.substring(shortUrl.length() - 6, shortUrl.length());
        return stl.get(tiny);
    }
    
    public String getTiny(int size) {
        String tiny = "";
        for (int i = 0; i < 6; i++) {
            tiny += dic[size%62];
            size /= 62;
        }
        return tiny;
    }
}

Solution 2: accepted 5ms

This solution will use more space but has better performance. 

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
public class Codec {
    
    private static HashMap<String, String> stl = new HashMap<>();
    private static HashMap<String, String> lts = new HashMap<>();
    private final String BASE_URL = "http://tinyurl.com/";
    private static char[] dic = {'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z','a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};
    
    // Encodes a URL to a shortened URL.
    public String encode(String longUrl) {
        int size = stl.size();
        String tiny = BASE_URL + getTiny(size); // store the leading url as well
        stl.put(tiny, longUrl);
        lts.put(longUrl, tiny);
        return tiny;
    }
    // Decodes a shortened URL to its original URL.
    public String decode(String shortUrl) {
        return stl.get(shortUrl);
    }
    
    public String getTiny(int size) {
        String tiny = "";
        for (int i = 0; i < 6; i++) {
            tiny += dic[size%62];
            size /= 62;
        }
        return tiny;
    }
}

Notes

Integer.toString(i, radix), 2 <= radix <= 36. For example, Integer.toString(11112222, 0) will give 6m68u.