Convert a non-negative integer to its english words representation. Given input is guaranteed to be less than $2^{31} - 1$.

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”

解题思路

略。

实现代码

// 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"};
};