CC150 17.7

17_7.cpp

/* CC150 17.7 */
// print an English phrase that describes the given integer
// http://en.wikipedia.org/wiki/English_numerals

#include <iostream>
#include <string>

using namespace std;

string digits[] = { "Zero",  "One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine" };
string teens[] = { "Ten", "Eleven", "Twelve", "Thirteen", "Fourteen", "Fifteen", "Sixteen", "Seventeen", "Eighteen", "Nineteen" };
string tens[] = { "", "", "Twenty", "Thirty", "Fourty", "Fifty", "Sixty", "Seventy", "Eighty", "Ninty" };
string bigs[] = { "", "Thousand", "Million", "Billion", "Trillion", "quadrillion" };

string numToString(int number)
{
	// negative number
	if (number < 0)
		return "Negative " + numToString(-number);
	// small number (0-99)
	if (number < 10) // [1, 9]
		return digits[number];
	else if (number < 20) // [10, 19]
		return teens[number % 10];
	else if (number < 100) { // [20, 99]
		string str = tens[number / 10];
		if (number % 10 != 0) // the second digit is not zero
			str += "-" + digits[number % 10];
		return str;
	}
	// median number (100-999)
	if (number < 1000) // [100, 999]
		return digits[number / 100] + " Hundred " + numToString(number % 100);
	// large number (1000-?)
	string str = "";
	int pow1k = 0;
	while (number % 1000 != 0) {
		str = numToString(number % 1000) + " " + bigs[pow1k++] + " " + str;
		number /= 1000;
	}
	return str;
}

int main()
{
	int n;
	cin >> n;
	cout << numToString(n) << endl;
	return 0;
}