在 C++ 中使用向量对数组进行排序时遇到问题

Question

我正在尝试制作一个用户输入学生姓名和考试成绩的程序。该程序将返回在曲线上评分的分数以及应获得该分数的学生的姓名。我遇到的问题是配对数组仅在下面输出 -858993460 是我的代码，感谢您的帮助。谢谢。

int main()
{
const int MAX = 300;
int n;
int y;
int x; // find what the difference between the highest score and 100
std::vector<std::pair < std::string, int>> vect;

//Asks for # of tests for loop
std::cout << "Hello, How many tests do you need to grade?" << std::endl;
std::cin >> n;
std::cout << "Please enter a grade then press enter. Repeat until you have 
reached the number specified in the previous step" << std::endl;
std::cout << "DO NOT ENTER DECIMALS" << std::endl;
// declare array
std::string name[MAX];
int score[MAX];

//pairs arrays
for (int i = 0; i < MAX; i++)
{
    vect.push_back(make_pair(name[i], score[i]));
}

// gets input for names and test scores
for (int i = 0; i < n; i++)
{
    std::cin >> name[i] >> score[i];


}




// sorts tests
std::sort(vect.begin(), vect.end()); 


//add a space for easier reading
std::cout << " " << std::endl;
//finds the difference between the highest scores and 0
x = 100 - vect[0].second;
for (int i = 0; i < n; i++)
{

    std::cout << vect[i].first << vect[i].second + x << std::endl;
}

std::cout << "enter a value then press enter to close";
    std::cin >> y;
return 0;
}

Answer 1

当您执行vect.push_back(make_pair(name[i], score[i])); 时，它会在数组中创建新对象，std::string name[MAX]; 和int score[MAX]; 没有引用。因此，当您输入std::cin >> name[i] >> score[i]; 时，您更改了name 数组和score 数组，您的向量(vect) 保持未初始化。 您需要创建临时的 std::pair < std::string, int> pair_input; 和 push_back 以在每次迭代时对其进行检查，如下所示：

// gets input for names and test scores
for (int i = 0; i < n; i++)
{
    std::pair < std::string, int> pair_input;
    std::cin >> pair_input.first >> pair_input.second;
    vect.push_back(pair_input);
}

删除之前初始化向量的部分推回：

//    //pairs arrays
//    for (int i = 0; i < MAX; i++)
//    {
//        vect.push_back(make_pair(name[i], score[i]));
//    }

因为我们会做 push_back 来向量化每个输入操作。完成所有更改后，您的代码如下所示：

#include <iostream>
#include <string>
#include <vector>
#include <iterator>

using namespace std;

int main()
{
    const int MAX = 300;
    int n;
    int y;
    int x; // find what the difference between the highest score and 100
    std::vector<std::pair < std::string, int>> vect;

    //Asks for # of tests for loop
    std::cout << "Hello, How many tests do you need to grade?" << std::endl;
    std::cin >> n;
    std::cout << "Please enter a grade then press enter. Repeat until you havereached the number specified in the previous step" << std::endl;
    std::cout << "DO NOT ENTER DECIMALS" << std::endl;

    // gets input for names and test scores
    for (int i = 0; i < n; i++)
    {
        std::pair < std::string, int> pair_input;
        std::cin >> pair_input.first >> pair_input.second;
        vect.push_back(pair_input);
    }

    // sorts tests
    std::sort(vect.begin(), vect.end());

    //add a space for easier reading
    std::cout << " " << std::endl;
    //finds the difference between the highest scores and 0
    x = 100 - vect[0].second;
    for (int i = 0; i < n; i++)
    {
        std::cout << vect[i].first << vect[i].second + x << std::endl;
    }

    std::cout << "enter a value then press enter to close";
    std::cin >> y;
    return 0;
}

我在测试时得到了这个输出结果：

Hello, How many tests do you need to grade?
2
Please enter a grade then press enter. Repeat until you havereached the number specified in the previous step
DO NOT ENTER DECIMALS
test
2
test3
3

test100
test3101
enter a value then press enter to close