#include<stdio.h>
#include<math.h>
int main()
{
double a,b,c,S=0,x=0;
scanf("%lf %lf %lf",&a,&b,&c);
if(a+b>c&&b+c>a&&a+c>b)
{
x=(a+b+c)/2.0;
S=sqrt(x*(x-a)*(x-b)*(x-c));
printf("%.3f\n",S);
}
else
printf("不能构成三角形\n");
return 0;
}

#include <stdio.h>
int main()
{
int x,y,z;
scanf("%d%d",&x,&y);
if(x>0)
{
if(y>0)
z=x*x+y*y;
else
z=x*x-y*y;
}
else
{
if(y>0)
z=x+y;
else
z=x-y;
}
printf("%d\n",z);
return 0;
}

#include <stdio.h>
int main()
{
int t;
scanf("%d",&t);
t=t/10;
switch (t)
{
case 10:
case 9 : printf("A\n");break;
case 8 : printf("B\n");break;
case 7 : printf("C\n");break;
case 6 : printf("D\n");break;
default: printf("E\n");break;
}
return 0;
}

#include <stdio.h>
int main()
{
int t;
scanf("%d",&t);
if(t>=90)
printf("A\n");
else if(t>=80)
printf("B\n");
else if(t>=70)
printf("C\n");
else if(t>=60)
printf("D\n");
else
printf("E\n");
return 0;
}

#include <stdio.h>
int main ()
{
int year;
scanf("%d",&year);
if((year%4==0)&&(year%100!=0)||(year%400==0))
printf("%d年是闰年\n",year);
else
printf("%d年不是闰年\n",year);
}

#include<stdio.h>
#include<math.h>
int main()
{
double a,b,c,d,e,f,t,x1,x2;
scanf("%lf %lf %lf",&a,&b,&c);
d=b*b-4*a*c;
e=-b/(2*a);
f=sqrt(fabs(d))/(2*a);
if(d>=0)
{x1=e+f;
x2=e-f;
if (x1>=x2)
printf("%.2f %.2f",x1,x2);
else
t=x1;
x1=x2;
x2=t;
printf("%.2f %.2f\n",x1,x2);
}
else
printf("%.2f+%.2fi %.2f-%.2fi\n",e,fabs(f),e,fabs(f));
}

ohshit，这是什么

#include<stdio.h>
#include<math.h>
#define PI 3.14
int main()
{
double r,s,sr;
int n;
scanf("%lf,%d",&r,&n);
s=n*r*r*sin(2*PI/n)/2;
sr=PI*r*r;
printf("yuan mian ji %lf nei jie %d bian xing mian ji %lf\n",sr,n,s);
return 0;
}

#include <stdio.h>
int main()
{
int n;
scanf("%d",&n);
switch(n){
case 1: printf("星期一"); break;
case 2: printf("星期二"); break;
case 3: printf("星期三"); break;
case 4: printf("星期四"); break;
case 5: printf("星期五"); break;
case 6: printf("星期六"); break;
case 7: printf("星期日"); break;
default: printf("Error!\n");
}
return 0;
}

#include <stdio.h>
int main()
{
int a,b,c,m,n,x;
scanf("%d %d",&m,&n);
x=0;
while(m<=n){
a=m/100;
b=m%100/10;
c=m%10;
if(m==a*a*a+b*b*b+c*c*c)
{
printf("%d ",m);
x++;
}
m++;
}
if(x==0)
printf("no\n");
return 0;
}

#include <stdio.h>
int main(void)
{
int x,y,i,j,k,sum,t;
while(scanf("%d%d",&x,&y)!=EOF)
{
sum=0;
if(x==0&&y==0) break;
for(i=x;i<=y;i++)
{
t=i*i+i+41;
k=1;
for(j=2;j*j<=t;j++)
{
if(t%j==0)
{
k=0;
break;
}
}
if(k)
sum++;
}
if(sum==y-x+1)
printf("OK\n");
else
printf("Sorry\n");
}
return 0;
}

#include<stdio.h>
int main(){
int a,d,n,sum=0;
scanf("%d %d %d",&a,&d,&n);
sum=n*a+d*n*(n-1)/2;
printf("%d\n",sum);
return 0;
}

#include<stdio.h>
int main()
{
int i,j,sum=1;
for(i=3;i<=1000;i++)
{ sum=1;
for(j=2;j<i;j++)
if( i%j==0) sum+=j;
if(i==sum)
printf("%d\n",i);
}
return 0;
}

#include<stdio.h>
int main()
{
int max,min,n,i,s,sum;
double ave;
while(scanf("%d",&n)!=EOF)
{
max=-1;min=101;sum=0;
for(i=0;i<n;i++)
{
scanf("%d",&s);
sum=sum+s;
if(max<s) max=s;
if(min>s) min=s;
}
ave=(sum-max-min)*1.0/(n-2);
printf("%0.2f\n",ave);
}
return 0;
}