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”

解題思路

略。

實現代碼

// Runtime: 8 ms
class Solution {
public:
    string numberToWords(int num) {
        return num2str(num);
    }

private:
    string num2str(int num)
    {
        string res = ;
        if (num <= 19)
        {
            res += nums[num];
        }
        else if (num <= 99)
        {
            res += tens[num / 10];
            if (num % 10 != 0)
            {
                res +=  ;
                res += num2str(num % 10);
            }
        }
        else if (num <= 999)
        {
            res += num2str(num / 100);
            res +=  Hundred;
            if (num % 100 != 0)
            {
                res +=  ;
                res += num2str(num % 100);
            }
        }
        else if (num <= 999999)
        {
            res += num2str(num / 1000);
            res +=  Thousand;
            if (num % 1000 != 0)
            {
                res +=  ;
                res += num2str(num % 1000);
            }
        }
        else if (num <= 999999999)
        {
            res += num2str(num / 1000000);
            res +=  Million;
            if (num % 1000000 != 0)
            {
                res +=  ;
                res += num2str(num % 1000000);
            }
        }
        else if (num <= 999999999999)
        {
            res += num2str(num / 1000000000);
            res +=  Billion;
            if (num % 1000000000 != 0)
            {
                res +=  ;
                res += num2str(num % 1000000000);
            }
        }

        return res;
    }

    string tens[10] = {, , Twenty, Thirty, Forty, Fifty, Sixty, Seventy, Eighty, Ninety};

    string nums[20] = {Zero, One, Two, Three, Four, Five, Six, Seven, Eight,
        Nine, Ten, Eleven, Twelve, Thirteen, Fourteen, Fifteen, Sixteen, Seventeen,
        Eighteen, Nineteen};
};