#include
  
   
#include
   
     #include
    
      #include
     
       //使用向量 ，就包含向量的头文件 #include
      
        #include
       
         using namespace std; int main() { cout << "please enter your first name :" << endl; string name; cin >> name; cout << "Hello " << name <<" !" << endl; cout << "please enter your midterm and final exam grades :" << endl; double midterm , final ; cin >> midterm >> final ; cout << "enter all your homework grades ." "followed by end-of-file :" << endl; vector
        
          homework; // 定义向量； double x; while(cin >> x) { homework.push_back(x); // 使用向量的好处是不用再像数组那样事先定义数组大小，因为向量可以动态增长； } typedef vector
         
          ::size_type vec_sz; //由于觉得size_type类型名太长，所以用另一个名字作为代替 ； vec_sz size = homework.size() ; // 这个函数可以求得向量里面元素的个数 if (size == 0){ cout << "endl" << "your must enter your greads ;" "please try again . " << endl; return 1; } sort(homework.begin() ,homework.end() ); // size函数的参数指定被排序的元素的范围，所以用到了这两个函数。begin指示第一个元素，end函指向紧跟在最后一个元素的之后的位置。 vec_sz mid = size/2; double median; median = size % 2 == 0 ? (homework[mid] + homework[mid - 1])/2 : homework[mid]; streamsize prec = cout.precision(); cout << "Your final grades is " << fixed << setprecision(3) << 0.2 * midterm + 0.4 * final +0.4 * median << setprecision(prec) << endl; return 0; }