短网址互转.go

package main

import "fmt"
import "strings"
import "math"

func main() {
	fmt.Println(get_num("r9"))
	fmt.Println(generate_code(840))
}

func get_num (code string) int {
    codes := "abcdefghjkmnpqrstuvwxyz23456789ABCDEFGHJKMNPQRSTUVWXYZ"
	num := 0
	i := len(code)
	codes_len := len(codes)
	
	for j:=0; j<len(code); j++ {
		i--
		char := string(code[j])
		pos := strings.Index(codes, char)
		tmp := math.Pow(float64(codes_len), float64(i))
		num += int(tmp) * (pos + 1)
	}
	num--
	return num
}

func generate_code (number int) string {
	var out = ""
	var key = 0
	codes := "abcdefghjkmnpqrstuvwxyz23456789ABCDEFGHJKMNPQRSTUVWXYZ"
	
	codes_len := len(codes)
	for {
		if number < codes_len {
			break
		}
		key = number % codes_len
		number = int(number / codes_len) - 1
		out = string(codes[key]) + out
	}
	return string(codes[number]) + out
}