# 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"

# Solution

Approach 1: Segment (every three digits) by segment.

# Code (Python)

Approach 1:

# Code (C++)

Approach 1:

class Solution {
private:
    string getSeg(int num) {
        string d00_19[] = {"", "One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine", "Ten", "Eleven", "Twelve", "Thirteen", "Fourteen", "Fifteen", "Sixteen", "Seventeen", "Eighteen", "Nineteen"};
        string d20_90[] = {"", "", "Twenty", "Thirty", "Forty", "Fifty", "Sixty", "Seventy", "Eighty", "Ninety"};
        ostringstream oss;
        // hundreds
        int hundreds = num / 100;
        if (hundreds > 0)
            oss << " " << d00_19[hundreds] << " Hundred";
        // tens
        int tens = num % 100;
        if (tens > 0 && tens < 20)
            oss << " " << d00_19[tens];
        else if (tens >= 20)
        {
            int digit = num % 10;
            oss << " " << d20_90[(tens-digit)/10];
            if (digit > 0)
                oss << " " << d00_19[digit];
        }
        return oss.str();
    }
public:
    string numberToWords(int num) {
        if (num == 0)
            return "Zero";
        string units[] = {"", " Thousand", " Million", " Billion"};
        string res = "";
        for (int i = 0; i < 4 && num; ++i)
        {
            string seg = getSeg(num % 1000);
            if (seg.size() > 0)
                res = seg + units[i] + res;
            num /= 1000;
        }
        return res.substr(1);
    }
};