C语言知识归纳I

 1 #include<stdio.h>
 2 int main()
 3 {
 4     int i = 0;
 5     int cnt = 0;
 6     int flag = 1; 
 7     int n = 0;
 8     double sum = 0;
 9     scanf("%d", &n);
10     for (i = 1; cnt < n; i += 3)
11     {
12         sum = sum + flag*(1.0 / i); //将数据从整型改为浮点型
13         cnt++;                      //增加次数
14         flag = -flag;               //改变符号
15     } 
16     printf("sum = %.3f\n", sum);    //保留小数点后三位
17     return 0;
18 }

#include<stdio.h>
int main()
{
    int a, b, c, max;
    scanf("%d %d %d", &a, &b, &c);//开始分别比较
    if (a > b) {
        max = a; a = b; b = max;  
    }
    if (a > c) {
        max = a; a = c; c = max;  //若上面if运行，则这里的a为原先b的值
    }
    if (b > c) {
        max = b; b = c; c = max;
    }
    printf("%d->%d->%d\n", a,b,c);
    return 0;
}

#include<stdio.h>
int main()
{
  int m,n;
  while(scanf("%d%d",&m,&n)!=EOF)   //运行到停止标记为止
  {
    int i,j,sum = 0,num = 0;
    if(m==n)                        //M和N相等的情况
    {
      j=2;
      while(j<m&&m%j!=0)j++;
      if(m==j)
        printf("1 %d\n",m);
      else
        printf("0 0\n");
      break;
    }
    for(i=m;i<=n;i++)              //M和N不想等的情况
    {
      j=2;
      while(j<i&&i%j!=0)j++;
      if(i==j)
      {
        num=num+1;
        sum=sum+i;
      }
    }
    printf("%d %d\n",num,sum);
  }
  return 0;
}