百钱百鸡:公鸡5元一只，母鸡3元一只，小鸡1元3只，100元要买100只鸡，共有几种情况

思路分析：
 1. x、y、z的取值范围为0~100
 2. x+y+z==100(鸡的总数为100)
 3. 5*x+3*y+z/3==100(钱的总数为100)
 4. z%3==0(小鸡只数是3的整数倍)

 

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

namespace buyChicken
{
    class Program
    {
        static void Main(string[] args)
        {
            int x, y, z;
            for (x = 0; x <= 100; x++)
            {
                for (y = 0; y <= 100; y++)
                {
                    for (z = 0; z <= 100; z++)
                    {
                        if ((5 * x + 3 * y + z / 3 == 100) && (x + y + z == 100) && (z % 3 == 0))
                        {
                            Console.Write("公鸡{0},母鸡{1},小鸡{2}\n", x, y, z);
                        }

                    }
                }
            }

    
            Console.ReadKey();
        }
    }
}