c# 经典521例（5）

将一个正整数分解质因数

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

namespace ConsoleApplication3
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.Write("请输入一个数字");
            int n= Convert.ToInt32(Console.ReadLine());
            for (int i = 2; i <= n; i++)
            {

                while (n != 1) 
                {
                    if (n % i == 0)
                    {
                        Console.WriteLine(i);
                        n = n / i;
                    }
                    else
                    { break; }
                }
            }
            Console.ReadLine();
        }

    }
}

输入两个正整数m和n，(利用辗除法)求其最大公约数和最小公倍数。

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

namespace ConsoleApplication3
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.Write("请输入第一个数字");
            int num1 = Convert.ToInt32(Console.ReadLine());
            Console.Write("请输入第二个数字");
            int num2 = Convert.ToInt32(Console.ReadLine());
            int a, b, temp, r;
            if (num1 < num2)
            {
                temp = num1;
                num1 = num2;
                num2 = temp;
            }
            a = num1; b = num2;
            while (b != 0)//利用辗除法，直到b为0为止
            {
                r = a % b;
                a = b;
                b = r;
            }
            Console.WriteLine("最大公约数为{0}",a);
            Console.WriteLine("最小公倍数为{0}", num1 * num2 / a);
            Console.ReadLine();
        }
    }
}

打印出如下图案（菱形）

        *

      *** 

   ******

  ********

   ****** 

     *** 

       *

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

namespace ConsoleApplication3
{
    class Program
    {
        static void Main(string[] args)
        {
            int i, j, k;
            for (i = 0; i <= 3; i++)
            {
                for (j = 0; j <= 2 - i; j++)
                    Console.Write(" ");
                for (k = 0; k <= 2 * i; k++)
                    Console.Write("*");
                Console.Write("\n");
            }
            for (i = 0; i <= 2; i++)
            {
                for (j = 0; j <= i; j++)
                      Console.Write(" ");
                for (k = 0; k <= 4 - 2 * i; k++)
                    Console.Write("*");
                  Console.Write("\n");
            }
            Console.ReadLine();
        }
    }
}

一个5位数，判断它是不是回文数。即12321是回文数，个位与万位相同，十位与千位相同

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

namespace ConsoleApplication3
{
    class Program
    {
        static void Main(string[] args)
        {
            int ge, shi, qian, wan;
            Console.Write("请输入一个五位数字");
            int x = Convert.ToInt32(Console.ReadLine());
            wan = x / 10000;
            qian = x % 10000 / 1000;
            shi = x % 100 / 10;
            ge = x % 10;
            if (ge == wan && shi == qian)/*个位等于万位并且十位等于千位*/
                Console.WriteLine("是回文数");
            else
                Console.WriteLine("不是回文数");
            Console.ReadLine();
        }
    }
}

求X的N次乘方 

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

namespace ConsoleApplication3
{
    class Program
    {
        static void Main(string[] args)
        {
            int t = 1;
            Console.WriteLine("请输入一个五位数字 ");
            int x = Convert.ToInt32(Console.ReadLine());
            Console.WriteLine("请输入次方数 ");
            int n = Convert.ToInt32(Console.ReadLine());
            for (int i = 1; i <= n; i++)
            {
                t = t * x;
            }
            Console.WriteLine("{0}的{1}次是：{2}", x, n, t);
            Console.ReadLine();
        }
    }
}