第二章 17-20

17.输出1—n之间所有素数，n为由键盘输入的数。

#include<stdio.h>

 

 

void main()

{

         int i,j,n,m=0;

         printf("请输入任意一个正整数:");

         scanf("%d",&n);

         for(i=1;i<=n;i+=2)

         {

        

                   for(j=2;j<=i;j++)

                            if(i%j==0)

                                     break;

                            if(j>=i)

                            {

                                     printf("%4d",i);

                                     m++;

                                     if(m%10==0)

                                     printf("\n");

                            }

                  

         }

         printf("\n");

 

}

18.输入一个正整数n，判断是否同时含有奇数和偶数字.

#include<stdio.h>

 

main()

{

         int n,temp,i=0,flag=0;

         printf("请输入一个正整数：");

         scanf("%d",&n);

    while(1)

    { temp=n%10;

      if(temp%2==0)

          {i++;}

     else

          {flag++;}

      n/=10;

     if(n==0)

      break;

    }

  if(i&&flag)

  {

          printf("YES\n");

  }

   else

   {

           printf("NO\n");

   }

 return 0;

}

19.输入一个数，判断其中的各位数字是否为奇偶交替出现。是输出YES,否输出NOT。

#include<stdio.h>

 

main()

{

         int i,n;

         printf("请输入一个正整数：");

         scanf("%d",&n);

         do

         {

                   i=n%10;

                   n=n/10;

                   if(i%2+n%10%2!=1)

                            break;

         }

         while(n);

                   if(n)

                   {

                            printf("NOT\n");

                   }

                   else

                   {

                            printf("YES\n");

                   }

}

20.工业总产值为200亿，平均每年增长4.5%，多少年总产值将超过500亿。

#include <stdio.h>

 

main()

{

   int i = 0;

   double n = 200.0;

   

   while (n<=500.0)

   {  

       n=n*1.045;

        i++;

   }  

   

   printf("%d\n", i);

   return 0;

}