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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