20165235 祁瑛 Java第四周考试总结

课后习题p29 p45

代码编写

import java.util.*;

class Example2_5{

  public static void main (String args[]){

     int start = 0,end ,middle;

     int a[] = {12,45,67,89,123,-45,67};

     int N = a.length;

     for(int i=0;i<N;i++){

     for(int j=i+1;j<N;j++){

       if(a[j] < a[i] ){

         int t = a[j];

         a[j] = a[i];

         a[i] = t;

       }

     }

   }

     Scanner scanner = new Scanner(System.in);

     System.out.println("输入一个整数，程序判断该数是否在数组中：");

     int number = scanner.nextInt();

     int count =0;

     end = N;

     middle=(start+end)/2;

     while(number!=a[middle]){

        if(number>a[middle])

          start = middle;

        else if (number < a[middle])

          end = middle;

        middle = (start+end)/2;

        count++;

        if(count>N/2)

          break;

   }

        if(count>N/2)

          System.out.printf("%d buzaishuzuzhong.\n",number);

        else

          System.out.printf("%d zaishuzuzhong.\n",number);

   }

}

public class Example3_7{

   public static void main (String args[]){

     int sum =0,i,j;

     for(i=1;i<=10;i++){

       if(i%2==0){

       continue;

     }

     sum=sum+i;

    }

     System.out.println("sum="+sum);

      for(j=2;j<=100;j++){

     for(i=2;i<=j/2;i++){

         if(j%i==0)

           break;

     }

       if(i>j/2){

     System.out.println(""+j+"是素数");

     }

   }

 }

}

在本次考试中因为我的截图上传失败，导致未能交上实验结果，可能是用QQ截图的原因。本次代码在第二周时已经敲好,如下为
p29代码连接
p45代码连接。
运行截图如下：

递归与循环

本次实验让我们通过编程实现1！+2！+3！+.....+n！的功能。代码如下：

 public class A{

     public static void main(String args[]){

      int [] a = new int [args.length];

      for(int i =0;i<args.length;i++){

         a[i] = Integer.parseInt(args[i]);

      }

      int sum = 0;

      if(args.length<1){

          System.out.println(" 输入有误！ ");

          System.exit(0);

        }

       for(int i =1;i<=a[0];i++){

          sum += fact(i);

        }

        if (sum<=0){

          System.out.println(" 输入有误！ ");

          System.exit(0);

        }

      System.out.println(sum);

  }

      public static int fact(int n) {

        if (n == 0)

            return 1;

        else

            return n * fact(n-1);

     }

}