どーも、みつおです。

英単語の定義がめんどくさい問題だった。

問題

1 から 5 までの数字を英単語で書けば one, two, three, four, five であり, 全部で 3 + 3 + 5 + 4 + 4 = 19 の文字が使われている.

では 1 から 1000 (one thousand) までの数字をすべて英単語で書けば, 全部で何文字になるか.

注: 空白文字やハイフンを数えないこと. 例えば, 342 (three hundred and forty-two) は 23 文字, 115 (one hundred and fifteen) は20文字と数える. なお, “and” を使用するのは英国の慣習.

出典：Problem17

解答

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Problem17
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine(Solve());
            Console.ReadLine();
        }

        private static int Solve()
        {
            int ret = 0;

            List<Number> numlist = new List<Number>();

            //1000までの数値と英単語を取得
            for (int i = 1; i <= 1000; i++)
            {
                Number num = new Number(i);
                numlist.Add(num);
            }

            //英単語の文字を足し合わせる
            foreach (var tmp in numlist)
            {
                ret += tmp.English.Length;
            }

            return ret;
        }
    }

    public class Number
    {
        #region プロパティ
        public int No { set; get; }

        public string English { set; get; }
        #endregion

        #region コンストラクタ
        public Number()
        {
            No = 0;
            English = "";
        }
        public Number(int no)
        {
            this.No = no;
            this.English = GetEnglish();
        }
        #endregion

        #region メソッド
        /// <summary>
        /// 数字を英単語に変換
        /// </summary>
        /// <returns></returns>
        public string GetEnglish()
        {
            string ret = "";
            int point = 0;

            string[] one = new string[] { "one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "ten", "eleven", "twelve", "thirteen", "fourteen", "fifteen", "sixteen", "seventeen", "eighteen", "nineteen" };
            string[] ten = new string[] { "twenty", "thirty", "forty", "fifty", "sixty", "seventy", "eighty", "ninety" };
            string[] hyaku = new string[] { "hundred", "thousand" };
            string and = "and";

            point = this.No;
            while (point != 0)
            {
                if (1 <= point && point <= 19)
                {
                    ret += one[point - 1];
                    point = 0;
                }
                else if (20 <= point && point <= 29)
                {
                    ret += ten[0];
                    point = point - 20;
                }
                else if (30 <= point && point <= 39)
                {
                    ret += ten[1];
                    point = point - 30;
                }
                else if (40 <= point && point <= 49)
                {
                    ret += ten[2];
                    point = point - 40;
                }
                else if (50 <= point && point <= 59)
                {
                    ret += ten[3];
                    point = point - 50;
                }
                else if (60 <= point && point <= 69)
                {
                    ret += ten[4];
                    point = point - 60;
                }
                else if (70 <= point && point <= 79)
                {
                    ret += ten[5];
                    point = point - 70;
                }
                else if (80 <= point && point <= 89)
                {
                    ret += ten[6];
                    point = point - 80;
                }
                else if (90 <= point && point <= 99)
                {
                    ret += ten[7];
                    point = point - 90;
                }
                else if (100 <= point && point <= 199)
                {
                    ret += one[0];
                    ret += hyaku[0];
                    point = point - 100;
                    if (point != 0) ret += and;
                }
                else if (200 <= point && point <= 299)
                {
                    ret += one[1];
                    ret += hyaku[0];
                    point = point - 200;
                    if (point != 0) ret += and;
                }
                else if (300 <= point && point <= 399)
                {
                    ret += one[2];
                    ret += hyaku[0];
                    point = point - 300;
                    if (point != 0) ret += and;
                }
                else if (400 <= point && point <= 499)
                {
                    ret += one[3];
                    ret += hyaku[0];
                    point = point - 400;
                    if (point != 0) ret += and;
                }
                else if (500 <= point && point <= 599)
                {
                    ret += one[4];
                    ret += hyaku[0];
                    point = point - 500;
                    if (point != 0) ret += and;
                }
                else if (600 <= point && point <= 699)
                {
                    ret += one[5];
                    ret += hyaku[0];
                    point = point - 600;
                    if (point != 0) ret += and;
                }
                else if (700 <= point && point <= 799)
                {
                    ret += one[6];
                    ret += hyaku[0];
                    point = point - 700;
                    if (point != 0) ret += and;
                }
                else if (800 <= point && point <= 899)
                {
                    ret += one[7];
                    ret += hyaku[0];
                    point = point - 800;
                    if (point != 0) ret += and;
                }
                else if (900 <= point && point <= 999)
                {
                    ret += one[8];
                    ret += hyaku[0];
                    point = point - 900;
                    if (point != 0) ret += and;
                }
                else if (1000 <= point && point <= 1999)
                {
                    ret += one[0];
                    ret += hyaku[1];
                    point = point - 1000;
                    if (point != 0) ret += and;
                }
            }

            return ret;
        }
        #endregion
    }
}

出力

21124