【LeetCode】273. Integer to English Words

Integer to English Words

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"

Show Hint 

 先把数字分割成4个三分位处理。前3个三分位分别加上Billion,Million,Thousand。

三分位处理函数为Helper()

class Solution {
public:
    string Helper(string numStr, string dict1[], string dict2[], string dict3[])
    {
        int num = atoi(numStr.c_str());
        if(num == 0)
            return "";
        else
        {
            string ret = "";
            int hundred = numStr[0] - '0';
            int ten = numStr[1] - '0';
            int one = numStr[2] - '0';
            
            if(hundred != 0)
                ret += dict1[hundred-1] + " Hundred";

            if(ten == 0)
            {
                if(one == 0)
                    return ret;
                else
                    return (ret=="")?(dict1[one-1]):(ret+" "+dict1[one-1]); 
            }
            else if(ten == 1)
            {
                return (ret=="")?(dict2[one]):(ret+" "+dict2[one]); 
            }
            else
            {
                if(one == 0)
                    return (ret=="")?(dict3[ten-2]):(ret+" "+dict3[ten-2]);
                else
                    return (ret=="")?(dict3[ten-2]+" "+dict1[one-1]):(ret+" "+dict3[ten-2]+" "+dict1[one-1]);
            }
        }
    }
    string numberToWords(int num) {
        if(num == 0)
            return "Zero";
        else
        {
            string ret = "";
            string dict1[9] = {"One","Two","Three","Four","Five","Six","Seven","Eight","Nine"};
            string dict2[10] = {"Ten","Eleven","Twelve","Thirteen","Fourteen","Fifteen","Sixteen","Seventeen",
                            "Eighteen","Nineteen"};
            string dict3[8] = {"Twenty","Thirty","Forty","Fifty","Sixty","Seventy","Eighty","Ninety"};

            string numStr = to_string(num);
            int len = numStr.size();
            string padding = string(12-len, '0');
            numStr = padding + numStr;

            string billionStr = Helper(numStr.substr(0,3), dict1, dict2, dict3);
            if(billionStr != "")
                ret += billionStr + " Billion";

            string millionStr = Helper(numStr.substr(3,3), dict1, dict2, dict3);
            if(millionStr != "")
                ret += (ret=="")?(millionStr+" Million"):(" "+millionStr+" Million");

            string thousandStr = Helper(numStr.substr(6,3), dict1, dict2, dict3);
            if(thousandStr != "")
                ret += (ret=="")?(thousandStr+" Thousand"):(" "+thousandStr+" Thousand");

            string oneStr = Helper(numStr.substr(9,3), dict1, dict2, dict3);
            if(oneStr != "")
                ret += (ret=="")?(oneStr):(" "+oneStr);
            return ret;
        }
    }
};