面试题 16.08. 整数的英语表示

链接：面试题 16.08. 整数的英语表示

class Solution {
public:
    std::vector<std::string> singles= {"", "One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine"};
    std::vector<std::string> teens = {"Ten", "Eleven", "Twelve", "Thirteen", "Fourteen", "Fifteen", "Sixteen", "Seventeen", "Eighteen", "Nineteen"};
    std::vector<std::string> tens = {"", "", "Twenty", "Thirty", "Forty", "Fifty", "Sixty", "Seventy", "Eighty", "Ninety"};
    std::vector<std::string> thousands = {"", "Thousand", "Million", "Billion"};
    string numberToWords(int num) {
        // 2^31 - 1 int最大值21亿
        if (num == 0) {
            return "Zero";
        }
        std::string sb;
        for (int i = 3, unit = 1000000000; i >= 0; --i, unit /= 1000) {
            int cur = num / unit;
            if (cur != 0) {
                sb += to_engish(cur) + thousands[i] + " ";
                num -= cur * unit;
            }
        }
        // 排出最后面的空格
        while (sb.back() == ' ') {
            sb.pop_back();
        }
        return sb;
    }
    std::string to_engish(int num) {
       // cout << num << endl;
        std::string sb;
        int houndred = num / 100;
        if (houndred !=0) {
            sb = singles[houndred] + " Hundred ";
        }
        num %= 100;
        cout << num << endl;
        int ten = num / 10;
        if (ten == 1) {       // cout << num << endl;
            // 这个地方是num-10
            sb += teens[num-10] + " ";
        //cout << num << endl;

            return sb;
        } else if (ten >= 2) { // 排出十位为0的情况
            sb += tens[ten] + " ";
        }
        num %= 10;
        cout << num << endl;
        // 排出个位为0的情况
        if (num != 0) {
            sb += singles[num] + " ";
        }
        return sb;
    }
};