Solution to Project Euler Problem 17: Number letter counts - If the numbers 1 to 5 are written out in words: one, two, three, four, five, then there are 3 + 3 + 5 + 4 + 4 = 19 letters used in total. If all the numbers from 1 to 1000 (one thousand) inclusive were written out in words, how many letters would be used? NOTE: Do not count spaces or hyphens. For example, 342 (three hundred and forty-two) contains 23 letters and 115 (one hundred and fifteen) contains 20 letters. The use of "and" when writing out numbers is in compliance with British usage.

• Java Code

package sikademy;
/**
 *
 * @author Archangel Macsika
 * Copyright (c) Sikademy. All rights reserved
 */

public class SikademyEulerSolution {
	
	public String run() {
		int sum = 0;
		for (int i = 1; i <= 1000; i++)
			sum += toEnglish(i).length();
		return Integer.toString(sum);
	}
	
	
	private static String toEnglish(int n) {
		if (0 <= n && n < 20)
			return ONES[n];
		else if (20 <= n && n < 100)
			return TENS[n / 10] + (n % 10 != 0 ? ONES[n % 10] : "");
		else if (100 <= n && n < 1000)
			return ONES[n / 100] + "hundred" + (n % 100 != 0 ? "and" + toEnglish(n % 100) : "");
		else if (1000 <= n && n < 1000000)
			return toEnglish(n / 1000) + "thousand" + (n % 1000 != 0 ? toEnglish(n % 1000) : "");
		else
			throw new IllegalArgumentException();
	}
	
	
	private static String[] ONES = {
		"zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine",
		"ten", "eleven", "twelve", "thirteen", "fourteen", "fifteen", "sixteen", "seventeen", "eighteen", "nineteen"};
	
	private static String[] TENS = {
		"", "", "twenty", "thirty", "forty", "fifty", "sixty", "seventy", "eighty", "ninety"};

	public static void main(String[] args) {
                SikademyEulerSolution solution = new SikademyEulerSolution();
		System.out.println(solution.run());
	}	
}

• Python Code

# 
# @author Archangel Macsika
# Copyright (c) Sikademy. All rights reserved.
# 

def compute():
	ans = sum(len(to_english(i)) for i in range(1, 1001))
	return str(ans)


def to_english(n):
	if 0 <= n < 20:
		return ONES[n]
	elif 20 <= n < 100:
		return TENS[n // 10] + (ONES[n % 10] if (n % 10 != 0) else "")
	elif 100 <= n < 1000:
		return ONES[n // 100] + "hundred" + (("and" + to_english(n % 100)) if (n % 100 != 0) else "")
	elif 1000 <= n < 1000000:
		return to_english(n // 1000) + "thousand" + (to_english(n % 1000) if (n % 1000 != 0) else "")
	else:
		raise ValueError()


ONES = ["zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine",
        "ten", "eleven", "twelve", "thirteen", "fourteen", "fifteen", "sixteen", "seventeen", "eighteen", "nineteen"]
TENS = ["", "", "twenty", "thirty", "forty", "fifty", "sixty", "seventy", "eighty", "ninety"]


if __name__ == "__main__":
	print(compute())