题目：

题解：

import "math/rand"type Codec map[int]stringfunc Constructor() Codec {return Codec{}
}func (c Codec) encode(longUrl string) string {for {key := rand.Int()if c[key] == "" {c[key] = longUrlreturn "http://tinyurl.com/" + strconv.Itoa(key)}}
}func (c Codec) decode(shortUrl string) string {i := strings.LastIndexByte(shortUrl, '/')key, _ := strconv.Atoi(shortUrl[i+1:])return c[key]
}