华为OJ之学英语

1、题目

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，长度不超过十位，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。

方法原型：public static String parse(long num)
2、这题目思路很简单，但是比较折腾人，很容易犯错。我看到题目的第一思路就是用个hashMap把不规则数字英语单词和对应的数字保存起来，然后根据输入的数字，根据个十百千万…位来取数字，然后加上billion、million、thousand、hundred and等词，由于英语数字有规律，3个为一组，可以加以利用；而且数字进行重复处理比较多，比如123，和23，它们都要输出23，所以最好写成函数来避免重复工作；还有就是我将英语数字1~20分成一组，为什么这样分因为前20个数没什么规律，比如twelve，而之后的数都有规律比如twenty
one。

3、代码写成之后要注意，一些特殊值得验证比如1000001,100,101。由于1
000 001中有连续3个0，这时在调用getThree(HashMap<String,String> map,long num)函数时要进行判断，否则容易输出 one million hundred and one。

4、代码

import java.util.HashMap;
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
String  str = scanner.nextLine();
if(str.matches("^[1-9][0-9]*$")){
long n = Long.parseLong(str);
System.out.println(parse(n));
}else{
System.out.println("error");
}
scanner.close();
}

public static String parse(long num){
HashMap<String,String> map = new HashMap<String,String>();
String str = "";
map.put("1", "one");
map.put("2", "two");
map.put("3", "three");
map.put("4", "four");
map.put("5", "five");
map.put("6", "six");
map.put("7", "seven");
map.put("8", "eight");
map.put("9", "nine");
map.put("10", "ten");
map.put("11","eleven");
map.put("12", "twelve");
map.put("13", "thirteen");
map.put("14", "fourteen");
map.put("15", "fifteen");
map.put("16", "sixteen");
map.put("17", "seventeen");
map.put("18", "eighteen");
map.put("19", "nighteen");
map.put("20", "twenty");
map.put("30", "thirty");
map.put("40", "forty");
map.put("50", "fifty");
map.put("60", "sixty");
map.put("70", "seventy");
map.put("80", "eighty");
map.put("90", "ninety");

if(num <= 20){
str = getOne(map,num);
}else if(num < 100){
str = getTwo(map,num);
}else if(num<1000){
str = getThree(map,num);
}else if(num <= 20000){
str = getFour(map,num);
}else if(num < 100000){
str = getFive(map, num);
}else if(num < 1000000){
str = getSix(map, num);
}else if(num <= 20000000){
str = getSeven(map, num);
}else if(num < 100000000){
str = getEight(map,num);
}else if(num < 1000000000){
str = getNine(map, num);
}else if(num <= 2147483647){
str = getTen(map, num);
}else{
str = "error";
}
return str;

}

public static String getOne(HashMap<String,String> map,long num){
if(num == 0){
return "";
}else
return map.get(num+"");
}

public static String getTwo(HashMap<String,String> map,long num){
if(num == 0){
return "";
}else if(num/10 == 0){
return getOne(map, num%10);
}else
return getOne(map,((num/10)*10))+ " " + getOne(map, num%10);
}

public static String getThree(HashMap<String,String> map,long num){

// 如果高位连续3位小于100，则必须以他们自身值作为百位，无需再除以100
if(num/100 <= 0){
if(num == 0){
return "";
}else if(num <= 20){
return "and "+getOne(map,num);
}else{
return "and "+getTwo(map, num);
}
}
else if(num % 100 == 0){
return getOne(map,num/100) +" hundred";
}else if(num % 100 < 20){
return getOne(map,num/100) +" hundred and "+ getOne(map,num%100);
}else{
return getOne(map,num/100) +" hundred and "+getTwo(map,num%100);

}
}

public static String getFour(HashMap<String,String> map,long num){
if(num/1000 == 0){
return getThree(map,num%1000);
}else
return getOne(map,num/1000) + " thousand " + getThree(map,num%1000);
}

public static String getFive(HashMap<String,String> map,long num){
if(num/1000 == 0){
return getThree(map,num%1000);
}else
return  getTwo(map,num/1000)+" thousand " + getThree(map,num%1000);
}

public static String getSix(HashMap<String,String> map,long num){
if(num/1000 == 0){
return getThree(map,num%1000);
}else
return getThree(map,num/1000) +" thousand "+getThree(map,num%1000);
}

public static String getSeven(HashMap<String,String> map,long num){
if(num/1000000 == 0){
return getSix(map, num%1000000);
}else
return getOne(map, num/1000000) +" million "+getSix(map, num%1000000);
}

public static String getEight(HashMap<String,String> map,long num){
if(num/1000000 == 0){
return getSix(map, num%1000000);
}else
return getTwo(map,num/1000000)+" million "+getSix(map, num%1000000);
}

public static String getNine(HashMap<String,String> map,long num){
if(num/1000000 == 0){
return getSix(map, num%1000000);
}else
return getThree(map, num/1000000)+" million "+getSix(map, num%1000000);
}

public static String getTen(HashMap<String,String> map,long num){
return getOne(map, num/1000000000) +" billion " + getNine(map, num%1000000000);
}
}

由于改错改了时间比较长，在此留下足迹，特此记之。