535. Encode and Decode TinyURL

Question

535. Encode and Decode TinyURL

Solution

题目大意:实现长链接加密成短链接,短链接解密成长链接

思路:加密成短链接+key,将长链接按key保存到map,解密时根据短链接提取key,再从map中返回长链接

Java实现:

1public class Codec {
2
3    // https://leetcode.com/problems/design-tinyurl --> http://tinyurl.com/4e9iAk
4    Map<Integer, String> map = new HashMap<>();
5    int i = 0;
6    
7    // Encodes a URL to a shortened URL.
8    public String encode(String longUrl) {
9        map.put(i, longUrl);
10        return "http://tinyurl.com/" + (i++);
11    }
12
13    // Decodes a shortened URL to its original URL.
14    public String decode(String shortUrl) {
15        int key = Integer.parseInt(shortUrl.substring(shortUrl.lastIndexOf("/") + 1));
16        return map.get(key);
17    }
18}
19
20// Your Codec object will be instantiated and called as such:
21// Codec codec = new Codec();
22// codec.decode(codec.encode(url));

Ref

https://leetcode.com/problems/encode-and-decode-tinyurl/discuss/100270/Three-different-approaches-in-java

Using simple counter

1public class Codec {
2    Map<Integer, String> map = new HashMap<>();
3    int i=0;
4    public String encode(String longUrl) {
5        map.put(i,longUrl);
6        return "http://tinyurl.com/"+i++;
7    }
8    public String decode(String shortUrl) {
9        return map.get(Integer.parseInt(shortUrl.replace("http://tinyurl.com/", "")));
10    }
11}

Using hashcode

1public class Codec {
2    Map<Integer, String> map = new HashMap<>();
3    public String encode(String longUrl) {
4        map.put(longUrl.hashCode(),longUrl);
5        return "http://tinyurl.com/"+longUrl.hashCode();
6    }
7    public String decode(String shortUrl) {
8        return map.get(Integer.parseInt(shortUrl.replace("http://tinyurl.com/", "")));
9    }
10}

Using random function

1public class Codec {
2    Map<Integer, String> map = new HashMap<>();
3    Random r=new Random();
4    int key=r.nextInt(10000);
5    public String encode(String longUrl) {
6        while(map.containsKey(key))
7            key= r.nextInt(10000);
8        map.put(key,longUrl);
9        return "http://tinyurl.com/"+key;
10    }
11    public String decode(String shortUrl) {
12        return map.get(Integer.parseInt(shortUrl.replace("http://tinyurl.com/", "")));
13    }
14}