0535. Encode and Decode TinyURL
https://leetcode.com/problems/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 a class to encode a URL and decode a tiny URL.
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.
Implement the Solution
class:
Solution()
Initializes the object of the system.String encode(String longUrl)
Returns a tiny URL for the givenlongUrl
.String decode(String shortUrl)
Returns the original long URL for the givenshortUrl
. It is guaranteed that the givenshortUrl
was encoded by the same object.
Example 1:
**Input:** url = "https://leetcode.com/problems/design-tinyurl"
**Output:** "https://leetcode.com/problems/design-tinyurl"
**Explanation:**
Solution obj = new Solution();
string tiny = obj.encode(url); // returns the encoded tiny url.
string ans = obj.decode(tiny); // returns the original url after deconding it.
Constraints:
1 <= url.length <= 104
url
is guranteed to be a valid URL.
ac
public class Codec {
String prefix = "http://tinyurl.com/";
String alphabet = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
Map<String, String> map = new HashMap<>();
Random random = new Random();
// Encodes a URL to a shortened URL.
public String encode(String longUrl) {
String key = getCode();
while (map.containsKey(key)) {
key = getCode();
}
map.put(key, longUrl);
return prefix+key;
}
// Decodes a shortened URL to its original URL.
public String decode(String shortUrl) {
return map.get(shortUrl.replace(prefix, ""));
}
private String getCode() {
StringBuilder sb = new StringBuilder();
for (int i = 0; i < 6; i++) {
sb.append(alphabet.charAt(random.nextInt(62)));
}
return sb.toString();
}
}
// Your Codec object will be instantiated and called as such:
// Codec codec = new Codec();
// codec.decode(codec.encode(url));
/*
3 ways: 1) simple counting; 2) hashCode(); 3) random of Alphabet, best.
*/
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