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.
C++:
class Solution {
public:
Solution() {
dict = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
short2long.clear();
long2short.clear();
srand(time(NULL));
}
// Encodes a URL to a shortened URL.
string encode(string longUrl) {
if (long2short.count(longUrl)) {
return "http://tinyurl.com/" + long2short[longUrl];
}
int idx = 0;
string randStr;
for (int i = 0; i < 6; ++i) randStr.push_back(dict[rand() % 62]);
while (short2long.count(randStr)) {
randStr[idx] = dict[rand() % 62];
idx = (idx + 1) % 5;
}
short2long[randStr] = longUrl;
long2short[longUrl] = randStr;
return "http://tinyurl.com/" + randStr;
}
// Decodes a shortened URL to its original URL.
string decode(string shortUrl) {
string randStr = shortUrl.substr(shortUrl.find_last_of("/") + 1);
return short2long.count(randStr) ? short2long[randStr] : shortUrl;
}
private:
unordered_map<string, string> short2long, long2short;
string dict;
};
