题解 | #学英语#

import javax.swing.*;
import java.util.*;
public class Main {
    public static void main(String[] args) {
        // 创建字典表
        Map<Integer, String> table = getTable();
        
        // 处理输入
        Scanner sc = new Scanner(System.in);
        long n = sc.nextLong();
        String ns = n + "";
        Deque<Character> stack = new LinkedList<>();
        for (char ch : ns.toCharArray()) {
            stack.push(ch);
        }
        
        // 从右到左提取三位数字
        int name = 0;  // 记录每个结束的三位数字的单位，0-无，1-thousand, 2-billion
        List<String> english = new ArrayList<>();  // 存储每三位的英语读法
        while (!stack.isEmpty()) {
            StringBuilder ansPart = new StringBuilder();
            StringBuilder sb = new StringBuilder();
            if (stack.size() >= 3) {
                sb.append(stack.pop());
                sb.append(stack.pop());
                sb.append(stack.pop());
                sb.reverse();
            } else if (stack.size() == 2) {
                sb.append(stack.pop());
                sb.append(stack.pop());
                sb.reverse();
            } else {
                sb.append(stack.pop());
            }
            // 获取到右边三位数字
            String part = sb.toString();
            int len = part.length();
            if (len == 3) {
                boolean flag = false;  // 判断第三位是否需要单独读取
                // 第一位有数字，输出英文加上" hundred"
                if (table.containsKey(part.charAt(0) - '0')) {
                    ansPart.append(table.get(part.charAt(0) - '0')).append(" hundred");
                }
                // 第二位有数字
                if (table.containsKey(part.charAt(1) - '0')) {
                    // 第三位需要单独读取
                    if (part.charAt(1) - '0' > 1) {
                        // 第一位有数字，需要加上"and "
                        if (table.containsKey(part.charAt(0) - '0')) {
                            ansPart.append(" and ");
                        }
                        ansPart.append(table.get((part.charAt(1) - '0') * 10));
                        flag = true;
                    } else {  // 第三位不需要单独读取
                        // 第一位有数字，需要加上"and "
                        if (table.containsKey(part.charAt(0) - '0')) {
                            ansPart.append(" and ");
                        }
                        int key = Integer.parseInt(part.substring(1, 3));
                        ansPart.append(table.get(key));
                    }
                } else {  // 第二位没有数字，第三位需要单独读取
                    flag = true;
                }
                // 第三位有数字
                if (table.containsKey(part.charAt(2) - '0') && flag) {
                    // 第二位有数字
                    if (table.containsKey(part.charAt(1) - '0')) {
                        ansPart.append(" ");
                    } else if (table.containsKey(part.charAt(0) - '0')) {
                        ansPart.append(" and "); // 第一位有数字，第二位没有数字，需要单独加" and "
                    }
                    ansPart.append(table.get(part.charAt(2) - '0'));
                }
            } else if (len == 2) {
                // 需要单独读取第二位
                if (part.charAt(0) - '0' > 1) {
                    // 第一位数字
                    if (table.containsKey(part.charAt(0) - '0')) {
                        ansPart.append(table.get((part.charAt(0) - '0') * 10));
                    }
                    // 第二位数字
                    if (table.containsKey(part.charAt(1) - '0')) {
                        // 第一位数字存在，第二位数字需要加上" "
                        if (table.containsKey(part.charAt(0) - '0')) {
                            ansPart.append(" ");
                        }
                        ansPart.append(table.get(part.charAt(1) - '0'));
                    }
                } else {  // 不需要单独读取第二位
                    ansPart.append(table.get(Integer.parseInt(part)));
                }
            } else if (len == 1) {
                ansPart.append(table.get(part.charAt(0) - '0'));
            }
            if (name == 1) {
                ansPart.append(" thousand");
            }
            if (name == 2) {
                ansPart.append(" million");
            }
            name++;
            // System.out.println(ansPart.toString());
            english.add(ansPart.toString());
        }

        for (int i = english.size() - 1; i >= 0; i--) {
            System.out.print(english.get(i));
            if (i != 0) {
                System.out.print(" ");
            }
        }
    }
    
    public static Map<Integer, String> getTable() {
        Map<Integer, String> table = new HashMap<>();
        table.put(1, "one");
        table.put(2, "two");
        table.put(3, "three");
        table.put(4, "four");
        table.put(5, "five");
        table.put(6, "six");
        table.put(7, "seven");
        table.put(8, "eight");
        table.put(9, "nine");
        table.put(10, "ten");

        table.put(11, "eleven");
        table.put(12, "twelve");
        table.put(13, "thirteen");
        table.put(14, "fourteen");
        table.put(15, "fifteen");
        table.put(16, "sixteen");
        table.put(17, "seventeen");
        table.put(18, "eighteen");
        table.put(19, "nineteen");

        table.put(20, "twenty");
        table.put(30, "thirty");
        table.put(40, "forty");
        table.put(50, "fifty");
        table.put(60, "sixty");
        table.put(70, "seventy");
        table.put(80, "eighty");
        table.put(90, "ninety");
        
        return table;
    }
}