0535. Encode and Decode TinyURL (M)

Encode and Decode TinyURL (M)

题目

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 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.

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题意

设计一个能将长URL和短URL互相转换的功能。

思路

无特定方法。

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代码实现

Java

public class Codec {
    private Map<String, String> toLong = new HashMap<>();
    private Map<String, String> toShort = new HashMap<>();
    private String pool = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
    private Random random = new Random();

    // Encodes a URL to a shortened URL.
    public String encode(String longUrl) {
        String suffix = randomSuffix(5);

        if (toShort.containsKey(longUrl)) {
            suffix = toShort.get(longUrl);
        } else {
            while (suffix == null || toLong.containsKey(suffix)) {
                suffix = randomSuffix(5);
            }
            toLong.put(suffix, longUrl);
            toShort.put(longUrl, suffix);
        }
        
        return "http://tinyurl.com/" + suffix;
    }

    // Decodes a shortened URL to its original URL.
    public String decode(String shortUrl) {
        return toLong.get(shortUrl.split("/", 4)[3]);
    }

    private String randomSuffix(int len) {
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < len; i++) {
            sb.append(pool.charAt(random.nextInt(62)));
        }
        return sb.toString();
    }
}