c++ - 如何在结构数组中显示学生姓名以及 GPA 高于平均水平的 ID

Question

我的任务是显示 GPA 高于平均水平的学生的姓名、ID、GPA。

#include <iostream>
#include <string>

using namespace std;

struct student{

    string name;
    char stdid[20];
    int age;
    char gender;
    float gpa;

};


int main() {

    int amount;
    float sum=0.0, average;

    struct student std[40];

    struct student *ptr = NULL;

    ptr = std;

    cout<<"enter the amount of students you want to input"<<endl;
    cin>>amount;


    for (int i=0;i<amount;i++)
    {
        cout<<"please enter details such as name, ID, age, gender and GPA for student "<< (i+1)<<endl;
        cout<<"Student ID : "<<endl;
        cin>>ptr->stdid;
        cout<<"Name : "<<endl;
        cin>>ptr->name;
        cout<<"Age : "<<endl;
        cin>>ptr->age;
        cout<<"Gender : "<<endl;
        cin>>ptr->gender;
        cout<<"GPA : "<<endl;
        cin>>ptr->gpa;
        sum += ptr->gpa;
    }

    average = sum/amount;
    cout << "Average GPA = " << average;


return 0;
}

例如，如果用户在程序中输入 3 个学生，例如；

学生 1:John，GPA 3.5

学生 2:Bob，GPA 4.0

学生 3:Mike，GPA 2.3

平均 GPA:3.23

然后输出将显示所有平均 GPA 高于 3.23 的学生的姓名、ID 和 GPA

Answer 1

我建议您考虑 std::vector用于存储 student 对象和算法的容器 std::accumulate()用于计算平均值:

std::vector<student> students;

// ...
// fill the vector of students
// ...

// calculate the sum of all GPAs
float sum = std::accumulate(students.begin(), students.end(), 0.0f,
                            [](float acc, const student& elem) {
                               return acc + elem.gpa;       
                            }
);

// calculate the average GPA
auto avg = sum / students.size();

要显示student 对象，您可以定义以下输出流运算符:

std::ostream& operator<<(std::ostream& os, student const& s) {
   os << s.stdid << " " << s.gpa << '\n';
}

然后，您可以遍历整个 student 对象集合并仅显示 GPA 高于平均水平的对象:

for (auto const& student: students)
   if (student.gpa > avg)
      std::cout << student; // call the output stream operator defined above