Leetcode 273 Integer to English Words

Convert a non-negative integer to its english words representation. Given input is guaranteed to be less than 231 - 1.

For example,

123 -> "One Hundred Twenty Three"
12345 -> "Twelve Thousand Three Hundred Forty Five"
1234567 -> "One Million Two Hundred Thirty Four Thousand Five Hundred Sixty Seven"

Solution 1: coding skill.

 public class Solution {  
   public String numberToWords(int num) {  
     String[] ones={"Zero","One","Two","Three","Four","Five","Six","Seven","Eight","Nine","Ten","Eleven","Twelve","Thirteen","Fourteen","Fifteen","Sixteen","Seventeen","Eighteen","Nineteen"};  
     String[] tens={"","","Twenty","Thirty","Forty","Fifty","Sixty","Seventy","Eighty","Ninety"};  
     String[] thousands={"Thousand","Million","Billion"};  
     int[] nums={1000,1000000,1000000000};  
     if (num<20) return ones[num];  
     if (num<100) return tens[num/10]+((num%10==0)?"":" "+ones[num%10]);  
     if (num<1000) return ones[num/100]+" Hundred"+((num%100==0)?"":" "+numberToWords(num%100));  
     for (int i=0; i<3; i++) {  
       if (i==2 || num<nums[i+1]) {  
         return numberToWords(num/nums[i])+" "+thousands[i]+((num%nums[i]==0)?"":" "+numberToWords(num%nums[i]));  
       }  
     }  
     return "";  
   }  
 }