笔试算法《学英语》

描述
Jessi初学英语，为了快速读出一串数字，编写程序将数字转换成英文：

如22：twenty two，123：one hundred and twenty three。

说明：

数字为正整数，长度不超过九位，不考虑小数，转化结果为英文小写；

输出格式为twenty two；

非法数据请返回“error”；

关键字提示：and，billion，million，thousand，hundred。

本题含有多组输入数据。

输入描述：
输入一个long型整数

输出描述：
输出相应的英文写法

示例1
输入：
2356

输出：
two thousand three hundred and fifty six

代码

public class Huawei学英语 {

    /**
     * 从右到左是2位，三位三位...之间一个and
     * @param args
     * @throws Exception
     */
    public static void main(String[] args) throws Exception {
        String[] numstr = new String[]{null, "one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "ten", "eleven", "twelve", "thirteen", "fourteen", "fifteen", "sixteen", "seventeen", "eighteen", "nineteen"};
        String[] teens = new String[]{null, null, "twenty", "thirty", "forty", "fifty", "sixty", "seventy", "eighty", "ninety"};
        String[] points = new String[]{"", "thousand", "million", "billion"};
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        String str;
        while((str = br.readLine()) != null) {
            char[] arr = str.toCharArray();
            int len = arr.length;
            StringBuilder sb = new StringBuilder();
            for(int i = (len - 1) / 3; i >= 0; i--) {
                int m = len - 1 - i * 3;
                int h = m < 2 ? 0 : (arr[m - 2] - '0');
                int t = (m < 1 ? 0 : ((arr[m - 1] - '0') * 10)) + arr[m] - '0';
                if(h == 0 && t == 0) {
                    continue;
                }
                if(t == 0 && sb.length() > 0) {
                    sb.append(" and");
                }
                if(h > 0) {
                    sb.append(' ').append(numstr[h]).append(" hundred");
                    if(t > 0)
                        sb.append(" and");
                }
                if(t > 20) {
                    sb.append(' ').append(teens[t / 10]);
                    if(t % 10 > 0)
                        sb.append(' ').append(numstr[t % 10]);
                } else if (t > 0) {
                    sb.append(' ').append(numstr[t]);
                }
                sb.append(' ').append(points[i]);
            }
            sb.deleteCharAt(0);
            System.out.println(sb.toString());
        }
    }


    /**
     * 方法二
     *
     * @param num
     * @return
     */
    public static String parse(int num){
        String[] numStr={"zero","one","two","three","four","five",
                "six","seven","eight","nine","ten","eleven","twelve",
                "thirteen","fourteen","fifteen","sixteen","seventeen",
                "eighteen","ninteen"};
        if(num>=0 && num<20){
            return numStr[num];
        }else if(num>=20 && num<100){
            int a=num%10;
            if(num<30){
                return a !=0?"twenty "+parse(a):"twenty";
            }else if(num<40){
                return a !=0?"thirty "+parse(a):"thirty";
            }else if(num<50){
                return a !=0?"forty "+parse(a):"forty";
            }else if(num<60){
                return a !=0?"fifty "+parse(a):"fifty";
            }else if(num<70){
                return a !=0?"sixty "+parse(a):"sixty";
            }else if(num<80){
                return a !=0?"seventy "+parse(a):"seventy";
            }else if(num<90){
                return a !=0?"eighty "+parse(a):"eighty";
            }else if(num<100){
                return a !=0?"ninety "+parse(a):"ninety";
            }
        }else if(num>=100 && num<1000){
            int x=num/100;
            int y=num%100;
            if(y!=0){
                return parse(x)+" hundred"+ " and "+ parse(y);
            }else{
                return parse(x)+" hundred";
            }
        }
        else if(num>=1000 && num<1000000){
            int x=num/1000;
            int y=num%1000;
            if(y!=0){
                return parse(x)+" thousand "+ parse(y);
            }else{
                return parse(x)+" thousand";
            }
        }else if(num>=1000000 && num<100000000){
            int x=num/1000000;
            int y=num%1000000;
            if(y!=0){
                return parse(x)+" million "+ parse(y);
            }else{
                return parse(x)+" million";
            }
        }
        return "error";
    }
}