利用62位的dict随机生成一个6位的字符串来作为短链接
dict=""abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890"";
for (int i=0; i<6; i++)
shortUrl+=dict[rand()%62];"构建short2long和long2short两个Map来存储长短链接之间的互换.
编码：
if (long2short.find(longUrl)!=long2short.end())
return "http://tinyurl.com/"+long2short[longUrl];
else
return "http://tinyurl.com/"+shortUrl;解码
string randStr = shortUrl.substr(shortUrl.find_last_of("/") + 1);
if (short2long.find(randStr)!=short2long.end())
longUrl = short2long[randStr];
else
longUrl = shortUrl;