算法---简单题(1)

    数据结构过阵子再搞算了，先重新复习下java书上的算法，花了两天的空余时间把java书上的例题自己又写了次，不过这次是用C#，其实差不多，这次比上次更娴熟了，大部分的简单题目都能看到题就能写下了，还有些不太熟悉的地方，也是C#语法上的，比如数组的维度，长度，行长，列长，这些区别都是google出来的，看来基础还是不行呢~继续加油。因为都是简单题目，所以就写到一个类里面了。

using System;

public class Java2Practice
{
    private readonly double PI=3.14;
    
    public void digSum(int i)
    {
       int a,b,c,digsum;
       a=i/100;
       b=(i%100)/10;
       c=i%10;
       digsum=a+b+c;
       Console.WriteLine(digsum);    
    }
    
    public void Circle_area(float i)
    {
       double area;
       area = PI*i*i;
       Console.WriteLine(area);
    }
    
    public void IsLeap(float i)
    {
       bool isLeap=false;
       isLeap=(i%4==0)||(i%400==0)&&(i%100!=0);
       Console.WriteLine(i+" is a leap,"+isLeap);
    }
     
    public void max3if(int a,int b,int c)
    {
       int max,min;
       if(a>b)
          max = a;
       else
          max = b;
       if(c>max)
          max = c;
       Console.Write("max = "+max+" ");
       min = a<b?a:b;
       min = c<min?c:min;
       Console.WriteLine("min = "+min+" ");
    }
     
    public void max3(int a,int b,int c)
    {
        if(a>b)
          if(b>c)
             Console.WriteLine(a+" "+b+" "+c);
          else
             if(c>a)
              Console.WriteLine(c+" "+a+" "+b);
             else
              Console.WriteLine(a+" "+c+" "+b);
         else
           if(c<a)
              Console.WriteLine(b+" "+a+" "+c);
           else
              if(b<c)
                Console.WriteLine(c+" "+b+" "+a);
              else
                Console.WriteLine(b+" "+c+" "+a);
    }

    public void sum_while(int i)
    {
       int sum=0,j=0;
       while(j<=i)
       {
          sum+=j;
          j++;
       }
       Console.WriteLine(sum);
    }

    public void fib_while(int i)
    {
        int a=0,b=1,count=0;
        while(count<=i)
        {
           Console.Write(a+" "+b+" ");
           a=a+b;
           b=a+b;
           count+=2; 
        }
        Console.WriteLine();    
    }
    
    public void sum_dowhile(int i)
    {
         int sum=0,j=0;
       do
       {
          sum+=j;
          j++;
       }while(j<=i);
       Console.WriteLine(sum);
    }
    //公式：gcd(a,b)=gcd(b,a%b) 
    public void gcd_dowhile(int a,int b)
    {
        int k=0;
        do{
           k=a%b;
           a=b;
           b=k;  
          }while(k!=0); 
        Console.WriteLine(a);
    }
    
    public void sum_for(int i)
    {
       int sum=0;
       for(int j=0;j<=i;j++)
       {
           sum+=j;
       }
       Console.WriteLine(sum);
    }
    
    public void week2(int y,int m,int d)
    {
       int total,week,i;
       bool leap = false;
       leap = (y%4==0)||(y%400==0)&&(y%100!=0);        week = 1;
       total = y-1980+(y-1980+3)/4;
       for(i=1;i<m;i++)
       {
            switch(i)
            {
               case 1:
               case 3:
               case 5: 
               case 7:
               case 8:
               case 10:
               case 12: 
                        total+=31;
                        break;
               case 4:
               case 6:
               case 9:
               case 11:
                        total+=30;
                        break;
               case 2:
                        if(leap)
                           total+=29;
                        else
                           total+=28;
                        break;
            }
        }
            total+=d;
            week =(week+total)%7;
            switch(week)
            {
                case 0:Console.Write("Sunday");
                       break;
                case 1:Console.Write("Monday");
                       break;
                case 2:Console.Write("Thuesday");
                       break;
                case 3:Console.Write("Wednesday");
                       break;
                case 4:Console.Write("Thursday");
                       break;
                case 5:Console.Write("Firday");
                       break;
                case 6:Console.Write("Saturday");
                       break;
            }
       }
     
    public void mul99()
    {
        int n=9;
        for(int i=0;i<=n;i++)
        {
             //Console.Write(i+" ");
             for(int j=1;j<=i;j++)
                Console.Write(i*j+"\t");
             Console.WriteLine();
        }
    } 
    
    public void prime_while()
    {
        const int Max = 50;
        int n=1,k=3;
        do{
          int j = (int)Math.Sqrt(k);
          if(j%2==0)
             j--;
          bool isPrime=true;
          while(j>2 && isPrime)
              if(k%j==0)
                isPrime=false;
              else
                j-=2;
          if(isPrime)
          {
             n++;
             Console.Write(k+" ");
          }
          k+=2;
          }while(k<=Max);

    }
 
    public void fib_array()
    {
        int[] fib = new int[8];
        fib[0]=0;
        fib[1]=1;
        for(int i=2;i<fib.Length;i++)
        {
             fib[i]=fib[i-1]+fib[i-2];
        }  
        for(int i=0;i<fib.Length;i++)
           Console.Write(fib[i]+" ");
    }
    
    public void prime_array()
    {
       const int Max = 50;
       int[] prime = new int[15];
       prime[0]=2;
       int n=1,k=3,i=1;
       do{
          int j=0;
          while(j<n && k%prime[j]!=0)
          {
               j++;
          } 
          if(j==n)
          {
             prime[i]=k;
             i++;
             n++;
          }
           k+=2;
         }while(k<=Max);
         for(int m=0;m<prime.Length;m++)
            Console.Write(prime[m]+" ");
    }

    public void helix_mat()
    {   
        int n=4,i,j,k=0;
        int[,] mat = new int[n,n];
        for(i=0;i<(n+1)/2;i++)
        {
            for(j=i;j<=n-i-1;j++)
                mat[i,j]=++k;
            for(j=i+1;j<=n-i-1;j++)
                mat[j,n-i-1]=++k;
            for(j=n-i-2;j>=i;j--)
                mat[n-i-1,j]=++k;
            for(j=n-i-2;j>=i+1;j--)
                mat[j,i]=++k;
        }
        output(mat);
    }

   public void Magic()
   {
      int n=3;
      int[,] mat = new int[n,n];
      int i=0,j=n/2;
      for(int k=1;k<=n*n;k++)
      {
            mat[i,j]=k;
            if(k%n==0)
                //i+=1;
               i=(i+1)%n;
            else
            {
                i=(i-1+n)%n;
                j=(j+1)%n;
            }
      }
      output(mat);
   }

   public void YangHui()
   {
        const int n = 5;
        int[][] mat = new int[n][];
        int i,j;
        for(i=0;i<n;i++)
        {
             mat[i]=new int[i+1];
             mat[i][0]=1;
             mat[i][i]=1;
             for(j=1;j<i;j++)
               mat[i][j]=mat[i-1][j-1]+mat[i-1][j];
        }

        for(i=0;i<mat.GetLength(0);i++)
        {
            for(j=0;j<n-i;j++)
               Console.Write(" ");
            for(j=0;j<mat[i].Length;j++)
               Console.Write("  "+mat[i][j]);
            Console.WriteLine();
        }
/*
       Console.WriteLine(mat.GetLength(0));
       for(int k=0;k<mat.Length;k++)
       Console.WriteLine(mat[k].Length);
*/
   }
   
   public void Rotor(string rotor)
   {
       rotor = rotor.ToLower();
       int len = rotor.Length;
       int i,j;
       bool isRotor = true;
       for(i=0,j=len-1;i<(len+1)/2;i++,j--)
       {
              if(rotor[i]!=rotor[j])
                  isRotor=false;
       }
       Console.Write(isRotor);
   }
   
   public void output(int[,] mat)
   {
      // Console.Write(mat.Length);  16
      // Console.Write(mat.Rank);  
       for(int i=0;i<mat.GetLength(0);i++)
        {
          for(int j=0;j<mat.GetLength(1);j++)
              Console.Write(mat[i,j]+"\t");
          Console.WriteLine();
        } 
   }



    public static void Main()
    {
       Java2Practice j2p = new Java2Practice();
       Console.Write("求一个3位数的数字和:");
       j2p.digSum(123);
       Console.Write("求圆的面积:");
       j2p.Circle_area(2.5f);
       Console.Write("判断是否闰年:");
       j2p.IsLeap(2009);
       Console.Write("判断3个数的最大数:");
       j2p.max3if(3,5,2);
       Console.Write("按从大到小排列3个数:");
       j2p.max3(3,5,2);
       Console.Write("while循环求和:");
       j2p.sum_while(10);
       Console.Write("输出fibonacci数列");
       j2p.fib_while(10);
       Console.Write("do-while循环求和:");
       j2p.sum_dowhile(10);
       Console.Write("辗转相除法求最大公因数:");
       j2p.gcd_dowhile(12,18);
       Console.Write("for循环求和:");
       j2p.sum_for(10);
       Console.Write("求某一天是星期几:");
       j2p.week2(2002,6,8);
       Console.Write("99乘法表:");
       j2p.mul99();
       Console.Write("求50以内的素数:");
       j2p.prime_while();
       Console.WriteLine();
       Console.Write("用一维数组求fibonacci数列:");
       j2p.fib_array();
       Console.WriteLine();
       Console.Write("用筛选法求50以内的素数:");
       j2p.prime_array();
       Console.WriteLine();
       Console.WriteLine("显示螺旋方阵:");
       j2p.helix_mat();
       Console.WriteLine("显示幻方:");
       j2p.Magic();
       Console.WriteLine("显示杨辉三角:");
       j2p.YangHui();
       Console.WriteLine();
       Console.Write("判断是否回文串:");
       j2p.Rotor("rottor");
    }
}

 

都是用得最常用的思路，以后再次复习的时候再想着怎么优化~没办法，现在水平低=。=囧