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Leetcode535. TinyURL的加密和解密

Leetcode535. TinyURL的加密和解密

作者: LonnieQ | 来源:发表于2019-11-15 00:44 被阅读0次

    题目

    TinyURL是一种URL简化服务, 比如:当你输入一个URL https://leetcode.com/problems/design-tinyurl 时,它将返回一个简化的URL http://tinyurl.com/4e9iAk.

    要求:设计一个 TinyURL 的加密 encode 和解密 decode 的方法。你的加密和解密算法如何设计和运作是没有限制的,你只需要保证一个URL可以被加密成一个TinyURL,并且这个TinyURL可以用解密方法恢复成原本的URL。

    思路

    给每个URL生成一个随机唯一的字符串,用两个哈希表,其中一个哈希表存储long url和short url的对应关系,另一个哈希表存储short url和long url的对应关系。

    C++代码

    #include <iostream>
    #include <vector>
    #include <map>
    #include <set>
    using namespace std;
    class Solution {
    public:
        vector<int> words;
        Solution() {
            for (char c = 'a'; c <= 'z'; c++) words.push_back(c);
            for (char c = 'A'; c <= 'Z'; c++) words.push_back(c);
            for (char c = '0'; c <= '9'; c++) words.push_back(c);
        }
        string baseURL = "http://tinyurl.com/";
        map<string, string> longToShorts, shortToLongs;
        // Encodes a URL to a shortened URL.
        string encode(string longUrl) {
            return getShortURLElseCreate(longUrl);
        }
        
        string getShortURLElseCreate(string longUrl) {
            string shortURL = "";
            if (longToShorts.count(longUrl)) shortURL = longToShorts[longUrl];
            else {
                do {
                    shortURL = baseURL;
                    for (int i = 0; i < 8; ++i) {
                        shortURL.push_back(words[rand() % words.size()]);
                    }
                } while (shortToLongs.count(shortURL));
                longToShorts[longUrl] = shortURL;
                shortToLongs[shortURL] = longUrl;
            }
            return shortURL;
        }
    
        // Decodes a shortened URL to its original URL.
        string decode(string shortUrl) {
            return shortToLongs[shortUrl];
        }
    };
    int main(int argc, const char * argv[]) {
        Solution solution;
        string url = "https://www.baidu.com";
        string longUrl, shortUrl;
        shortUrl = solution.encode(url);
        cout << shortUrl << endl;
        cout << solution.decode(shortUrl) << endl;
        return 0;
    }
    

    来源:力扣(LeetCode)
    链接:https://leetcode-cn.com/problems/encode-and-decode-tinyurl

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