题解 | #学英语#

package main

import (
	"bufio"
	"fmt"
	"io"
	"os"
	"strconv"
	"strings"
)

func main() {
	// map: key = num, value = word
	m := make(map[int]string)
	m[1] = "one"
	m[2] = "two"
	m[3] = "three"
	m[4] = "four"
	m[5] = "five"
	m[6] = "six"
	m[7] = "seven"
	m[8] = "eight"
	m[9] = "nine"
	m[10] = "ten"
	m[11] = "eleven"
	m[12] = "twelve"
	m[13] = "thirteen"
	m[14] = "fourteen"
	m[15] = "fifteen"
	m[16] = "sixteen"
	m[17] = "seventeen"
	m[18] = "eighteen"
	m[19] = "ninteen"
	m[20] = "twenty"
	m[30] = "thirty"
	m[40] = "forty"
	m[50] = "fifty"
	m[60] = "sixty"
	m[70] = "seventy"
	m[80] = "eighty"
	m[90] = "ninety"
	// input
	inputReader := bufio.NewReader(os.Stdin)
	for {
		// handle input
		input, err := inputReader.ReadString('\n')
		if err == io.EOF {
			break
		}
		input = strings.Trim(input, "\r\n")
		if input == "0" {
			fmt.Println(0)
			continue
		}

		// 从右边开始，每三个数字为一组，split -> arr
		arr := make([]int, 0)

		if len(input) < 2 { // 只有一位
			input0, _ := strconv.Atoi(string(input[0]))
			arr = append(arr, input0)
		} else if len(input) > 1 { // 十位 + 个位
			input1, _ := strconv.Atoi(string(input[len(input)-2:]))
			arr = append(arr, input1)
		}
		if len(input) > 2 { // 百位
			input2, _ := strconv.Atoi(string(input[len(input)-3]))
			arr = append(arr, input2)
		}
		if len(input) == 4 { // 最高千位
			input3, _ := strconv.Atoi(string(input[0]))
			arr = append(arr, input3)
		}
		if len(input) > 4 { // 万位 + 千位
			input4, _ := strconv.Atoi(string(input[len(input)-5 : len(input)-3]))
			arr = append(arr, input4)
		}
		if len(input) > 5 { // 十万位
			input5, _ := strconv.Atoi(string(input[len(input)-6]))
			arr = append(arr, input5)
		}
		if len(input) == 7 { // 百万位
			input6, _ := strconv.Atoi(string(input[0]))
			arr = append(arr, input6)
		}

		// 从右边开始，加word
		res := ""
		for i := 0; i < len(arr); i++ {
			if arr[i] == 0 {
				continue
			}
			if i == 0 { // 十位 + 个位
				if arr[i] < 20 {
					res = m[arr[i]]
				} else {
					gewei := arr[i] % 10
					shiwei := arr[i] - gewei
					res = m[shiwei] + " " + m[gewei]
				}
			}
			if i == 1 { // 百位
				if arr[i] == 0 {
					continue
				}
				if arr[0] == 0 {
					res = m[arr[i]] + " hundred" + res
				} else {
					res = m[arr[i]] + " hundred and " + res
				}
			}
			if i == 2 { // 万位 + 千位
				if arr[i] == 0 {
					continue
				}
				if arr[i] < 20 {
					res = m[arr[i]] + " thousand " + res
				} else {
					gewei := arr[i] % 10
					shiwei := arr[i] - gewei
					if gewei == 0 {
						res = m[shiwei] + " thousand " + res
					} else {
						res = m[shiwei] + " " + m[gewei] + " thousand " + res
					}
				}
			}
			if i == 3 { // 十万位
				if arr[2] == 0 {
					res = m[arr[i]] + " hundred " + res
				} else {
					res = m[arr[i]] + " hundred and " + res
				}
			}
			if i == 4 { // 百万位
				res = m[arr[i]] + " million " + res
			}
		}
		fmt.Println(res)
	}
}