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);
     }
}