LeetCode-Encode and Decode TinyURL

1. Encode and Decode TinyURL（Medium）

Description[/i]

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.

Analysis[/i]

编码部分，使用字符串hash函数，将longUrl哈希获得

size_t

类型的值，将

size_t

值hash转换为字符串str，然后将该字符串和

longUrl

放入

map <string, string> url

中，返回

"http://tinyurl.com/" + str

；

解码部分，截取

shortUrl

的后一部分，将其作为

key

来获取

url

中的对应长地址。

代码：

class Solution {
public:

// Encodes a URL to a shortened URL.
string encode(string longUrl) {
size_t hash = hash_fn(longUrl);
string str = to_string(hash);
url.insert(map<string , string>::value_type(str, longUrl));
return "http://tinyurl.com/" + str;
}

// Decodes a shortened URL to its original URL.
string decode(string shortUrl) {
auto pos = shortUrl.find_last_of("/");
return url[shortUrl.substr(pos + 1)];
}

private:
map <string, string> url;
std::hash<std::string> hash_fn;
};