1.比较三个数的大小：

#include<stdio.h>
int main(void)
{
	int a,b,c,max;
	scanf("%d%d%d",&a,&b,&c);
	if(a>=b) {
		if(a>=c) max=a;
		else max=c;
	}else{
		if(b>=c) max =b;
		else max=c;
	}printf("max=%d",max);
	return 0;
}

2.高速公路超速处罚：

#include<stdio.h>
int main(void)
{
	int limit,x;
	scanf("%d%d",&limit,&x);
	 if(x>=(limit+limit*0.5))  printf("吊销驾驶证"); 
	  else if(x>=(limit+limit*0.1)) printf("罚款200元");
	return 0;
}

3.出租车计价：

#include<stdio.h>
int main(void)
{
	//输入行驶里程和分钟 
   int x,y,price1=0,price2=0;
   scanf("%d%d",&x,&y);
   //控制时间 
   if(y>=5){
   	int a=y;
   	while(a>=5) {
   		price2+=2;
   		a/=10;
	   }
   }
   //控制里程
   if(x<=3) price1 =10;
   else if(x<=10) price1 =10+(x-3)*2;
   else if(x>10) price1 =10+14+(x-10)*3;
   printf("%d",price1+price2); 
	return 0;
}

4.统计学生成绩：

#include<stdio.h>
int main(void)
{
    int  i ,n;
    char score;
	scanf("%d",&n);
	int arr[n];
	 for(i=0;i<n;i++){
	 	scanf("%d",&arr[i]);
	 	if(arr[i]>=90) printf("score = A");
	 	else if(arr[i]<90&&arr[i]>=80) printf("score = B");
	 	else if(arr[i]<80&&arr[i]>=70) printf("score = C");
	 	else if(arr[i]<70&&arr[i]>=60) printf("score = D");
	 	else printf("score = E");
	 }
	return 0;
}

5.三角形判断：

#include<stdio.h>
#include<math.h>
int main(void)
{
   double a,b,c,s,C,area;
   int x1,y1,x2,y2,x3,y3;
   scanf("%lf%lf%lf%lf%lf%lf",&x1,&y1,&x2,&y2,&x3,&y3);
   a=sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
   b=sqrt((x3-x2)*(x3-x2)+(y3-y2)*(y3-y2));
   c=sqrt((x1-x3)*(x1-x3)+(y1-y3)*(y1-y3));
   if((a+b>c)&&(a+c>b)&&(b+c>a)){
   	C=a+b+c;
   	s=(a+b+c)/2;
   	area=sqrt(s*(s-a)*(s-b)*(s-c));
   	printf("C=%.2f area=%.2f",C,area);
   }
   else printf("Impossible"); 
	return 0;
}