Integer to English Words

Problem: Integer to English Words

In this problem, we can divide digits into group of three and deal with each group first than do with thousand, million or billion. Besides, we need to deal with 0 too.

Code in Python:

class Solution(object):
    def numberToWords(self, num):
        """
        :type num: int
        :rtype: str
        """
        dict1 = ["", "One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine"]
        dict2 = ["", "", "Twenty", "Thirty", "Forty", "Fifty", "Sixty", "Seventy", "Eighty", "Ninety"]
        dict3 = ["Ten", "Eleven", "Twelve", "Thirteen", "Fourteen", "Fifteen", "Sixteen", "Seventeen", "Eighteen", "Nineteen"]
        dict4 = ["Thousand", "Million", "Billion"]

        def helper(num):
            ans = ""
            if num == 0: return ans
            if num/100 != 0:
                ans += dict1[num/100] + " Hundred "
                num = num % 100
            if num >= 10 and num < 20: ans += dict3[num-10] + " "
            else:
                if num/10 != 0:
                    ans += dict2[num/10] + " "
                    num = num % 10
                if num != 0:
                    ans += dict1[num] + " "
            return ans

        if not num: return "Zero"
        i, ans = 0, ""
        ans = helper(num%1000) + ans
        while num/1000:
            num = num / 1000
            if num % 1000 != 0:
                ans = helper(num%1000) + dict4[i] + " " + ans
            i += 1
        return ans[:len(ans)-1]