用C#求：用一张1元换1分、2分和5分的硬币，问有几种换法？每种换发中1分、2分和5分的硬币各几枚？新手的我觉得很难呀！

static void Main (string[] args)
        {
            ArrayList x_1 = new ArrayList();
            ArrayList x_2 = new ArrayList();
            ArrayList x_5 = new ArrayList();
            int i, j, k;
            int sum =0;
            int count = 0;
            for (i = 0; i < 101; i++)
            {
                for (j = 0; j < 51; j++)
                {
                    for (k = 0; k < 21; k++)
                    {
                        sum = i + 2 * j + 5 * k;

                        if (sum == 100)
                        {
                            x_1.Add(i);
                            x_2.Add(j);
                            x_5.Add(k);
                            count++;
                        }
                        if(sum >100)
                        {
                            break;
                        }
                    }
                }
            }
            Console.Write("一共有几种分法： ");
            Console.WriteLine(count);
            for (int g = 0; g < count; g++ )
            {
                Console.Write(x_1[g] + ", ");
                Console.Write(x_2[g] + ", ");
                Console.Write(x_5[g] + "; |");
                if (g>0 && g % 6 == 0)
                {
                    Console.WriteLine();
                }
            }
            Console.ReadLine();

        }

前面部分出错了

你要引用命名空间 System.Collections,就是在程序开始加上 Using System.Collections

还是不行！我做得这个有点问题，帮忙修改一下！

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

namespace _99
{
    class Program
    {
        static void Main(string[] args)
        {
            int i = 0;
            int j = 0;
            int l = 0;
            int m = 0;
            for (i = 0; i <= 100; i++)
            {
                for (j = 0; j <= 50; j++)
                {
                    for (l = 0; l <= 20; l++)
                    {
                        if (5 * l + 2 * j + i == 100)
                        {
                            m = m + 1;
                            Console.WriteLine("这种换法共需要一分钱{0}个，两分钱{1}个，五分钱{2}个", i, j, l);
                        }
                    }
                }
                Console.WriteLine("共{0}种换法", m);
            }
        }
    }
}

static void Main(string[] args)
        {
            int i = 0;
            int j = 0;
            int l = 0;
            int m = 0;
            for (i = 0; i <= 100; i++)
            {
                for (j = 0; j <= 50; j++)
                {
                    for (l = 0; l <= 20; l++)
                    {
                        if (5 * l + 2 * j + i == 100)
                        {
                            m = m + 1;
                            Console.WriteLine("这种换法共需要一分钱{0}个，两分钱{1}个，五分钱{2}个", i, j, l);
                        }
                    }
                }
            }
            Console.WriteLine("共{0}种换法", m);
            Console.ReadLine();
        }