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.

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"

class Solution(object):
    def numberToWords(self, num):
        """
        :type num: int
        :rtype: str
        """
        if num==0:
            return 'Zero'
        l1 = ['','One ','Two ','Three ','Four ','Five ','Six ','Seven ','Eight ','Nine ']
        l2 = ['Ten ','Eleven ','Twelve ','Thirteen ','Fourteen ','Fifteen ','Sixteen ','Seventeen ','Eighteen ','Nineteen ']
        l3 = ['','','Twenty ','Thirty ','Forty ','Fifty ','Sixty ','Seventy ','Eighty ','Ninety ']
        l4 = ['','Hundred ','Thousand ','Million ','Billion ']
        s = str(num)
        def solve(n,i):
            res = ''
            if n=='000':
                return res
            if n[0] != '0':
                res += l1[int(n[0])] + l4[1]
            if n[1] == '1':
                res += l2[int(n[2])%10]
            else:
                res += l3[int(n[1])] + l1[int(n[2])]
            return res + l4[i]
        s = '0' * (12-len(s)) + s
        output = solve(s[0:3],4) + solve(s[3:6],3) + solve(s[6:9],2) + solve(s[9:12],0)
        return output.rstrip()

tip:补到同样的12位方便处理