题解 | #学英语#

package main

import (
	"fmt"
	"strings"
)

var (
    hash = map[int]string{
        0: "",
        1: "thousand",
        2: "million",
        3: "billion",
    }
    num = map[byte]string{
        '1': "one",
        '2': "two",
        '3': "three",
        '4': "four",
        '5': "five",
        '6': "six",
        '7': "seven",
        '8': "eight",
        '9': "nine",
    }
    tens = map[string]string{
        "10": "ten",
        "11": "eleven",
        "12": "twelve",
        "13": "thirteen",
        "14": "fourteen",
        "15": "fifteen",
        "16": "sixteen",
        "17": "seventeen",
        "18": "eighteen",
        "19": "nineteen",
        "2" : "twenty",
        "3" : "thirty",
        "4" : "forty",
        "5" : "fifty",
        "6" : "sixty",
        "7" : "seventy",
        "8" : "eighty",
        "9" : "ninety",
        "0": "",
    }
)

func main() {
    str := ""
    fmt.Scan(&str)
    if  len(str)% 3 != 0 {
        n := len(str)
        for i := 0; i < 3 - (n % 3); i++ {
            str = "0" + str
        }
    }

    ans := ""

    count := 0
    for part := str[len(str)-3:]; len(str) != 0; str = str[:len(str)-3] {
        part = str[len(str)-3:]
        tmp := convert(part)
        ans = strings.Join([]string{tmp,hash[count],ans}, " ")
        count++
    }
    
    fmt.Println(ans)
}

func convert(str string) string {
    res := ""
    if s, ok := num[str[0]]; ok {
        res += s + " hundred "
        if str[1:] != "00" {
            res +=  "and "
        }
    }

    if str[1] == '1' {
        res += tens[str[1:]]
        return res
    }
    res += tens[str[1:2]]
    if str[1] != '0' && str[2] != '0' {
        res += " " 
    }

    return res + num[str[2]]
}