题解 | #学英语#

import java.util.Scanner;
import java.util.Map;
import java.util.HashMap;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static String result = "";
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextLong()) { // 注意 while 处理多个 case
            Long a = in.nextLong();
            StringBuffer sb = new StringBuffer();
            toEnglish(a, sb);
            System.out.println(sb.toString());
        }
    }
    public static void toEnglish(long input, StringBuffer sbbuffer) {
        Map<Integer, String> numberMap = new HashMap<>();
        numberMap.put(1, "one"); numberMap.put(2, "two"); numberMap.put(3, "three");
        numberMap.put(4, "four"); numberMap.put(5, "five"); numberMap.put(6, "six");
        numberMap.put(7, "seven"); numberMap.put(8, "eight"); numberMap.put(9, "nine");
        numberMap.put(10, "ten"); numberMap.put(11, "eleven"); numberMap.put(12, "twelve");
        numberMap.put(13, "thirteen"); numberMap.put(14, "fourteen"); numberMap.put(15, "fifteen");
        numberMap.put(16, "sixteen"); numberMap.put(17, "seventeen"); numberMap.put(18, "eighteen");
        numberMap.put(19, "nineteen"); numberMap.put(20, "twenty"); numberMap.put(30, "thirty");
        numberMap.put(40, "forty"); numberMap.put(50, "fifty"); numberMap.put(60, "sixty");
        numberMap.put(70, "seventy"); numberMap.put(80, "eighty"); numberMap.put(90, "ninety");
        if (input <= 20) {
            int temp = (int)input;
            sbbuffer.append(numberMap.get(temp));
            return;
        }
        if (input < 100) {
            int shiwei = (int)input / 10;

            if (input % 10 == 0) {
               sbbuffer.append(numberMap.get(shiwei * 10));
                return;
            }
            sbbuffer.append(numberMap.get(shiwei * 10) + " ");
            toEnglish(input % 10, sbbuffer);
            return;
        }
        if (input < 1000) {
            int baiwei = (int)input / 100;
            if (input % 100 == 0) {
                sbbuffer.append(numberMap.get(baiwei) + " hundred");
                return;
            }
            sbbuffer.append(numberMap.get(baiwei) + " hundred").append(" and ");
            toEnglish(input % 100, sbbuffer);
            return;
        }
        if (input < 1000000) {
            int qianwei = (int)(input / 1000);
            toEnglish(input / 1000, sbbuffer);
            sbbuffer.append(" thousand ");
            toEnglish(input % 1000, sbbuffer);
            return;
        }
        if (input < 1000000000) {
            int gaowei = (int)(input / 1000000);
            toEnglish(input / 1000000, sbbuffer);
            sbbuffer.append(" million ");
            toEnglish(input % 1000000, sbbuffer);
            return;
        }
    }
}