using System;

namespace ConsoleSimpleSuanFa
{
    /// <summary>    
    ///     C#简单算法（循环，递归）
    ///     LDH @ 2021-4-12
    /// </summary>
    internal class Program
    {
        private static void Main()
        {
            Console.Title = "C#中简单循环和递归示例";

            var calculator = new Calculator();

            Console.WriteLine("【循环实现】从10到1输出如下：");
            calculator.PrintXTo1(10);
            PrintLine();

            Console.WriteLine("【递归实现】从10到1输出如下：");
            calculator.PrintXToOne(10);
            PrintLine();

            Console.WriteLine($"【循环实现】从1-100的和：{calculator.SumFrom1ToX(100)}");
            PrintLine();

            Console.WriteLine($"【递归实现】从1-100的和：{calculator.SumFromOneToX(100)}");
            PrintLine();

            Console.ReadKey();
        }

        /// <summary>
        ///     完美分割线
        /// </summary>
        private static void PrintLine()
        {
            Console.WriteLine("—————————————————— 我是最完美的分割线 ——————————————————");
        }
    }

    internal class Calculator
    {
        /// <summary>
        ///     从指定数字到1输出【循环实现】
        /// </summary>
        /// <param name="x">指定数字</param>
        public void PrintXTo1(int x)
        {
            for (var i = x; i > 0; i--) Console.WriteLine(i);
        }

        /// <summary>
        ///     从指定数字到1输出【递归实现】
        /// </summary>
        /// <param name="x">指定数字</param>
        public void PrintXToOne(int x)
        {
            if (x == 1)
            {
                Console.WriteLine(x);
            }
            else
            {
                Console.WriteLine(x);
                PrintXToOne(x - 1);
            }
        }

        /// <summary>
        ///     从1指定数字的和【循环实现】
        /// </summary>
        /// <param name="x">指定数字</param>
        public int SumFrom1ToX(int x)
        {
            var sum = 0;
            for (var i = 0; i < x + 1; i++) sum += i;

            return sum;
        }

        /// <summary>
        ///     从1指定数字的和【递归实现】
        /// </summary>
        /// <param name="x">指定数字</param>
        public int SumFromOneToX(int x)
        {
            if (x == 1) return 1;

            var sum = x + SumFromOneToX(x - 1);
            return sum;
        }
    }
}