學英語

題目描述

Jessi初學英語，爲了快速讀出一串數字，編寫程序將數字轉換成英文：
如22：twenty two，123：one hundred and twenty three。

說明
數字爲正整數，長度不超過十位，不考慮小數，轉化結果爲英文小寫；
輸出格式爲twenty two；
非法數據請返回「error」；
關鍵字提示：and，billion，million，thousand，hundred。

方法原型：public static String parse(long num)

輸入描述:

輸入一個long型整數

輸出描述:

輸出相應的英文寫法

輸入例子:

2356

輸出例子:

two thousand three hundred and fifty six

算法實現

import java.util.Scanner;

/**
 * Declaration: All Rights Reserved !!!
 */
public class Main {

    private final static String WORDS[] = {
            "", "one", "two", "three", "four", "five",// 1-5
            "six", "seven", "eight", "nine", "ten",// 6-10
            "eleven", "twelve", "thirteen", "fourteen", "fifteen",// 11-15
            "sixteen", "seventeen", "eighteen", "nineteen", "twenty",// 16-20
            "thirty", "forty", "fifty", "sixty", "seventy", "eighty", "ninety"// 30-90
    };

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
//        Scanner scanner = new Scanner(Main.class.getClassLoader().getResourceAsStream("data.txt"));
        while (scanner.hasNextLong()) {
            long num = scanner.nextLong();
            System.out.println(parse(num));
        }
        scanner.close();
    }

    private static String parse(long num) {
        if (num <= 0) {
            return "error";
        } else if (num < 20) {  // 20如下
            return WORDS[(int) num];
        } else if (num < 100) {
            if (num % 10 == 0) {
                return WORDS[(int) (20 + (num - 20) / 10)];     // 20 30 40 50 60 70 80 90
            } else {
                return parse(num / 10 * 10) + " " + parse(num % 10);
            }
        } else if (num < 1_000) { // 千如下
            if (num % 100 == 0) {
                return parse(num / 100) + " hundred";
            } else {
                return parse(num / 100) + " hundred and " + parse(num % 100);
            }
        } else if (num < 1_000_000) { // 百萬如下
            if (num % 1_000 == 0) {
                return parse(num / 1_000) + " thousand";
            } else {
                return parse(num / 1_000) + " thousand " + parse(num % 1_000);
            }
        } else if (num < 1_000_000_000) { // 億
            if (num % 1_000_000 == 0) {
                return parse(num / 1_000_000) + " million";
            } else {
                return parse(num / 1_000_000) + " million " + parse(num % 1_000_000);
            }
        } else if (num < 10_000_000_000L) { // 十億
            if (num % 1_000_000_000 == 0) {
                return parse(num / 1_000_000_000) + " billion";
            } else {
                return parse(num / 1_000_000_000) + " billion " + parse(num % 1_000_000_000);
            }
        } else {
            return "error";
        }
    }
}