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:
public class Codec {
// https://leetcode.com/problems/design-tinyurl --> http://tinyurl.com/4e9iAk
Map<Integer, String> map = new HashMap<>();
int i = 0;
// Encodes a URL to a shortened URL.
public String encode(String longUrl) {
map.put(i, longUrl);
return "http://tinyurl.com/" + (i++);
}
// Decodes a shortened URL to its original URL.
public String decode(String shortUrl) {
int key = Integer.parseInt(shortUrl.substring(shortUrl.lastIndexOf("/") + 1));
return map.get(key);
}
}
// Your Codec object will be instantiated and called as such:
// Codec codec = new Codec();
// codec.decode(codec.encode(url));
Ref
Using simple counter
public class Codec {
Map<Integer, String> map = new HashMap<>();
int i=0;
public String encode(String longUrl) {
map.put(i,longUrl);
return "http://tinyurl.com/"+i++;
}
public String decode(String shortUrl) {
return map.get(Integer.parseInt(shortUrl.replace("http://tinyurl.com/", "")));
}
}
Using hashcode
public class Codec {
Map<Integer, String> map = new HashMap<>();
public String encode(String longUrl) {
map.put(longUrl.hashCode(),longUrl);
return "http://tinyurl.com/"+longUrl.hashCode();
}
public String decode(String shortUrl) {
return map.get(Integer.parseInt(shortUrl.replace("http://tinyurl.com/", "")));
}
}
Using random function
public class Codec {
Map<Integer, String> map = new HashMap<>();
Random r=new Random();
int key=r.nextInt(10000);
public String encode(String longUrl) {
while(map.containsKey(key))
key= r.nextInt(10000);
map.put(key,longUrl);
return "http://tinyurl.com/"+key;
}
public String decode(String shortUrl) {
return map.get(Integer.parseInt(shortUrl.replace("http://tinyurl.com/", "")));
}
}