學英語

/*

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) 
 
 
 
知識點	字符串,循環,函數,指針,枚舉,位運算,結構體,聯合體,文件操作,遞歸
運行時間限制	10M
內存限制	128
輸入	
輸入一個long型整數
輸出	
輸出相應的英文寫法
樣例輸入	2356
樣例輸出	two thousand three hundred and fifty six

*/


import java.util.Scanner;

public class Main {

	public static void main(String args[])
	{
		Scanner sca = new Scanner(System.in);

		String str = sca.next();
		sca.close();
		
		if(!str.matches("0|[1-9][0-9]*"))
		{
			return;
		}
		long number = Long.parseLong(str);
		if(number > 9999999999L)
		{
			return;
		}
		System.out.println(parse(number));
	}
	
	public static String parse(long num) 
	{
		String temp = Long.toString(num);
		String english = "";
		int n = 0;
		if(temp.length()%3 == 0)
		{
			n = temp.length()/3;
		}
		else
		{
			n = temp.length()/3 + 1;
		}
		
		String[] str = new String[n];
		for(int i = 0; i < n; i++)
		{
			if(i != n-1)
				str[i] = temp.substring(temp.length()-(i+1)*3,temp.length()-i*3);
			else
				str[i] = temp.substring(0,temp.length()-i*3);
			
		}
		
		for(int i = n-1; i >= 0; i--)
		{
			english += word(str[i],i+1);
		}
		
		return english;
	}
	
	public static String word(String num,int symbol)
	{
		int number = Integer.parseInt(num);
		String english = "";
		
		String[] unit = {"","one","two","three","four","five","six","seven","eight","nine"};
		String[] ten = {"","eleven","twelve","thirteen","fourteen","fifteen","sixteen","seventeen","eighteen","ninteen"};
		String[] decade = {"","ten","twenty","thrity","forty","fifty","sixty","seventy","eighty","ninety"};
		
		switch(num.length())
		{
		case 1:
			english = unit[number];
			break;
		case 2:
			if(number%10 != 0)
			{
				if(number/10 != 1)
					english = decade[number/10]+" "+unit[number%10];
				else
					english = ten[number%10];
			}
			else
				english = decade[number/10];
			break;
		case 3:
			if(number/100 != 0)
			{
				if(number%100 != 0)
					english = unit[number/100]+" hundred and "+ word(Integer.toString(number%100),1);
				else 
					english = unit[number/100]+" hundred";
			}
			else
			{
				if(number%100 != 0)
					english = "and "+word(Integer.toString(number%100),1);
			}
			
			break;
		}
		switch(symbol)
		{
		case 1:
			break;
		case 2:
			if(number != 0)
				english += " thousand ";
			break;
		case 3:
			if(number != 0)
				english += " million ";
			break;
		case 4:
			if(number != 0)
				english += " billion ";
			break;
		}
		return english;
	}
}

寫這個的時候腦細胞死了一大堆啊……