我不知道如何用变量写平均成绩

Question

我正在尝试自动设置给定变量的数量，例如：

char subject1[30];
char subject2[30];
char subject3[30];
float grade1;
float grade2;
float grade3;

cout << "Type in your first subject: "  ;
cin >> subject1;
cout << "Type in your second subject: ";
cin >> subject2;
cout << "Type in your third subject: ";
cin >> subject3;

cout << "Type in your grade for: " << subject1 << " :";
cin >> grade1;
cout << "Type in your grade for: " << subject2 << " :";
cin >> grade2;
cout << "Type in your grade for: " << subject3 << " :";
cin >> grade3;


float sum = grade1 + grade2 + grade3;
float average = (sum / 3);


cout << "AVERAGE GRADE";
cout << "************************************" << endl;
cout << subject1 << grade1 << endl;
cout << subject2 << grade2 << endl;
cout << subject3 << grade3 << endl;
cout << "====================================" << endl;
cout << "Average: " << average << endl;

return 0;

计算它的代码有效，但是我想知道如何输入用户输入的3个等级。因此，我不必在每次添加另一个主题时都去编辑计算部分。我不确定我的意思是否解释正确，但希望您能理解。

Answer 1

一种简单的解决方案是将所有内容存储在vector中（大多数情况下，这比您所使用的char array更为可取），然后循环查找所拥有的主题数。

#include <vector>   // need to inlcude this to be able to use vector
#include <iostream>

const int numSubjects = 3;

std::vector<std::string> prefix{"first", "second", "third"};
std::vector<std::string> subjects(numSubjects);
std::vector<float> grades(numSubjects);

for(int i = 0; i < numSubjects; i++) {
    std::cout << "Type in your " << prefix[i] << " subject: ";
    std::cin >> subjects[i];
    std::cout << "Type in your grade for " << subjects[i] << ": ";
    std::cin >> grades[i];
}

//afterwards do the calculations

[请注意，我用numSubjects的大小初始化了向量，以便您可以使用[]运算符访问和写入向量的索引。如果不使用大小初始化vector，则可以使用push_back()插入元素。