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  • 535. Encode and Decode TinyURL

    package LeetCode_535
    
    /**
     * 535. Encode and Decode TinyURL
     * https://leetcode.com/problems/encode-and-decode-tinyurl/description/
     *
     * 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.
     * */
    class Codec() {
        /*
        * solution, Two HaspMap
        * */
        private val BASE_URL = "http://tinyurl.com/"
        //total 62 characters for generate short_url
        val chatSet = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
        //key is long url,value short url
        val mapShortUrl = HashMap<String, String>()
        //key is short url,value long url
        val mapLongUrl = HashMap<String, String>()
    
        // Encodes a URL to a shortened URL.
        fun encode(longUrl: String): String {
            if (mapShortUrl.containsKey(longUrl)) {
                return mapShortUrl.get(longUrl) ?: ""
            }
            var key = ""
            do {
                val sb = StringBuilder()
                for (i in 0..6) {
                    val r = (Math.random() * chatSet.length).toInt()
                    sb.append(chatSet[r])
                }
                key = sb.toString()
                //if contains key, keep doing generate
            } while (mapShortUrl.containsKey(longUrl))
            val url = BASE_URL + key
            mapShortUrl.put(longUrl, url)
            mapLongUrl.put(url, longUrl)
            return url
        }
    
        // Decodes a shortened URL to its original URL.
        fun decode(shortUrl: String): String {
            return mapLongUrl.getOrDefault(shortUrl, "")
        }
    }
    /**
     * Your Codec object will be instantiated and called as such:
     * var obj = Codec()
     * var url = obj.encode(longUrl)
     * var ans = obj.decode(url)
     */
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  • 原文地址:https://www.cnblogs.com/johnnyzhao/p/13721893.html
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