c++ - 如何在 C++ 中以结构体中的数组为目标

Question

所以我编写了一个程序来使用结构和数组来计算文件中学生的最高/最低成绩(很快就会成为平均成绩)。虽然我确实计算出了最低和最高成绩，但我还想添加哪个学生的成绩最高和最低。我如何找到数组行并显示结构的 .first 和 .last？

#include <iostream>
#include <string>
#include <fstream>
#include <array>

using namespace std;

struct student {

    int id;
    string first;
    string last;
    float grade;
};

string getFileName();
void fillArrayFromFile(ifstream&, student[], int&);
float calculateMaximumGrade(student[], int);
float calculateMinimumGrade(student[], int);
float calculateAverageGrade(student[], int);



int main() {

    int numofStudents = 5;

    const int NUM_VALS = 5;

    student studentArray[NUM_VALS];
    ifstream filename;
    //filename.open(getFileName() + ".txt");

    fillArrayFromFile(filename, studentArray, numofStudents);

cout << "Highest grade: " << calculateMaximumGrade(studentArray,     numofStudents) << endl;
cout << "Lowest grade: " << calculateMinimumGrade(studentArray, numofStudents) << endl;
//cout << "Average grade: " << calculateAverageGrade(studentArray, numofStudents) << endl;

return 0;
}

string getFileName()
{
// To be completed

return 0;
}

void fillArrayFromFile(ifstream& ins, student studentArray[], int&   numberOfStudents)
{
ins.open("input.txt");



for (int i = 0; i < numberOfStudents; i++) {

    ins >> studentArray[i].id;
    ins >> studentArray[i].first;
    ins >> studentArray[i].last;
    ins >> studentArray[i].grade;

}

ins.close();

return;
}

// calculate the maximum grade in the array
float calculateMaximumGrade(student studentArray[], int numberOfStudents)
{
float max = 0;
max = studentArray[0].grade;

for (int i = 0; i < numberOfStudents; i++) {

    if (studentArray[i].grade > max) {

        max = studentArray[i].grade;

    }

}
return max;
}

// calculate the minimum grade in the array
float calculateMinimumGrade(student studentArray[], int numberOfStudents)
{
float min = 0;
min = studentArray[0].grade;

for (int i = 0; i < numberOfStudents; i++) {

    if (studentArray[i].grade < min) {

        min = studentArray[i].grade;

    }

}
return min;
}

// calculate the average grade in the array
float calculateAverageGrade(student studentArray[], int numberOfStudents)
{
// To be completed
return 0;
}

Answer 1

您不仅需要在 calculateMaximumGrade 函数中存储 max，还需要存储具有该 max 等级的元素的索引。即:

int calculateMaximumGrade(student studentArray[], int numberOfStudents)
{
    float max = studentArray[0].grade;
    int index_of_max = 0;

    for (int i = 0; i < numberOfStudents; i++) {

        if (studentArray[i].grade > max) {
            index_of_max = i;
            max = studentArray[i].grade;
        }

    }
    return index_of_max;
}

如您所见，您也可以不返回max，而是返回它的index。然后你应该在你的 main 中执行以下操作:

int index_of_max = calculateMaximumGrade(studentArray,     numofStudents);
cout << "Highest grade: " << studentArray[index_of_max].grade << ". Student, who got it: " << studentArray[index_of_max].first << " " << studentArray[index_of_max].last << endl;

您应该对 Average 和 Min 函数执行相同的操作。