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

# include<stdio.h>

int main(void)
{
 double a, b, c;
 double t;
 printf("输入三个浮点数（中间以空格区分）：");
 scanf("%lf %lf %lf", &a, &b, &c);
 if (a > b)
  t = a;
 else
  t = b;

 if (t > c)
  printf("最大值是%lf\n", t);
 else
  printf("最大值是%lf\n", c);

 return 0;
}

刚学一个星期 应该没错