Note: This is a companion problem to the System Design problem:Design TinyURL-System/).
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.
要求将长URL转化为短URL,即通过长URL可以生成短URL,短URL也可以找到长URL。
通过Map结构就可以实现,只需要将长URL和短URL之间的映射分别进行存储即可。
private Map<String, String> longToShortUrl = new HashMap<>(); private Map<String, String> shortToLongUrl = new HashMap<>(); private static final String SHORT\_URL\_PREFIX \= "http://tinyurl.com/"; private static final String AVAILABLE_CHARACTERS = "1234567890qwertyuiopasdfghjklzxcvbnm"; private Random random = new Random(); // Encodes a URL to a shortened URL. public String encode(String longUrl) { if (longToShortUrl.containsKey(longUrl)) { return SHORT_URL_PREFIX + longToShortUrl.get(longUrl); } String result; do{ result = getRandomShortUrl(6); } while (shortToLongUrl.containsKey(result)); longToShortUrl.put(longUrl, result); shortToLongUrl.put(result, longUrl); return SHORT_URL_PREFIX + result; } // Decodes a shortened URL to its original URL. public String decode(String shortUrl) { String shortRandomCharacters = shortUrl.replace(SHORT_URL_PREFIX, ""); return shortToLongUrl.get(shortRandomCharacters); } private String getRandomShortUrl(int length) { StringBuilder sb = new StringBuilder(); while (length-- > 0) { int randomIndex = (int)(Math.random() * AVAILABLE_CHARACTERS.length()); sb.append(AVAILABLE_CHARACTERS.charAt(randomIndex)); } return sb.toString(); }