Question

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

Example 1:

Input: 123
Output: "One Hundred Twenty Three"
Example 2:

Input: 12345
Output: "Twelve Thousand Three Hundred Forty Five"
Example 3:

Input: 1234567
Output: "One Million Two Hundred Thirty Four Thousand Five Hundred Sixty Seven"
Example 4:

Input: 1234567891
Output: "One Billion Two Hundred Thirty Four Million Five Hundred Sixty Seven Thousand Eight Hundred Ninety One"

Solution

  • Method 1: 
    class Solution {
    private static String[] bigUnit = new String[]{"", "Thousand", "Million", "Billion"};
    private static String[] numbers = new String[]{"", "One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine"};
    private static String[] tens = new String[]{"", "Ten", "Twenty", "Thirty", "Forty", "Fifty", "Sixty", "Seventy", "Eighty", "Ninety"};
    private static String[] overTens = new String[]{"", "Eleven", "Twelve", "Thirteen", "Fourteen", "Fifteen", "Sixteen", "Seventeen", "Eighteen", "Nineteen"};
    public String numberToWords(int num) {
        if(num == 0) return "Zero";
        String result = "";
        int bigUnitIndex = 0;
        while(num > 0){
            String temp = parseThree(num % 1000);
            if(temp.length() != 0){
                result = temp
                + (bigUnitIndex == 0 ? "": " ")
                + bigUnit[bigUnitIndex]
                + (result.length() == 0 ? "": " ") + result;
            }
            bigUnitIndex++;
            num /= 1000;
        }
        return result;
    }
    private String parseThree(int num){
        String res = "";
        if(num % 100 > 10 && num % 100 < 20){
            res = overTens[num % 100 - 10];
            num /= 100;
        }else{
            if(num % 10 != 0){
                res = numbers[num % 10];
            }
            num /= 10;
            if(num % 10 != 0){
                res = tens[num % 10] + (res.length() == 0 ? "":" ") + res;
            }
            num /= 10;
        }
        if(num % 10 != 0){
            res = numbers[num % 10] + " Hundred" + (res.length() == 0 ? "": " ") + res;
        }
        return res;
    }
}