最大值和最小值显示为真而不是数字，我该怎么办？

问题描述

我需要数组中的最小和最大数字，但它告诉我函数的地址将始终为真，而不是数字。我不知道该更改什么。

#include <iostream>

using namespace std;

int main()
{
    double num1[10] {0.61,1.70,0.52,1.34,0.25,1.20,0.46,1.10,1.68,1.37}; //material used in february
    double total1 {0};
    float average1 {0};
    int i;

    for (i=0; i<10; i++)
    {
        total1 = total1 + num1[i];
    }

    average1 = total1/10.0; //average of material used in feb

    double max1(double num1); // maximum of material used in feb

    double min1(double num1); // minimum of material used in feb

    cout << "Maximum is " << max1 << endl;
    cout << "Average is " << average1 << endl;
    cout << "Minimum is " << min1 << endl;


    double num2[10] {1.64,1.15,1.63,0.93,0.51,1.13,1.16,1.56,1.38}; //material used in march
    double total2 {0};
    float average2 {0};
    int l;

    for (l=0; l<10; l++)
    {
        total2 = total2 + num2[l];
    }

    average2 = total2/10.0; //average of material used in march
    
    double max2(double num1); // maximum of material used in march

    double min2(double num1); // minimum of material used in march 

    cout << "Maximum is " << max2 << endl;
    cout << "Average is " << average2 << endl;
    cout << "Minimum is " << min2 << endl;

    return 0;

}

解决方法

这里您没有打印最大值，而是要打印一个函数指针，该指针将隐式转换为bool。永远不会nullptr，所以永远是true。

// These two lines are actually forward-declarations of two functions
// called max1 and min1.
double max1(double num1);
double min1(double num1);

cout << "Maximum is " << max1 << endl; // printing function pointer here
cout << "Average is " << average1 << endl;
cout << "Minimum is " << min1 << endl; // printing function pointer here

您需要的是：

#include <algorithm>
#include <numeric>
#include <array>

int main()
{
    constexpr std::array<double,10> num1 {
        0.61,1.70,0.52,1.34,0.25,1.20,0.46,1.10,1.68,1.37
    };

    double *max1 = std::max_element(std::begin(num1),std::end(num1));
    double *min1 = std::min_element(std::begin(num1),std::end(num1));
    double avg1 = std::accumulate(std::begin(num1),std::end(num1),0.0)
                  / num1.size();

    // Note that we only need std::endl if we want to flush std::cout.
    // Otherwise '\n' is enough.
    std::cout << "Maximum is " << *max1 << '\n';
    std::cout << "Minimum is " << *min1 << '\n';
    std::cout << "Average is " << avg1 << '\n';

    // ...
}

std::min_element返回一个指向范围内最小值的指针（在您的情况下为数组）。

std::begin和std::end将迭代器返回到数组的开头和结尾。这适用于std::array和C样式的数组。

还要注意，std::accumulate可用于轻松计算总和。您无需自己为此编写循环。

---

有关迭代器和指针以及它们之间的区别的更多信息，请参见Iterator = pointer? Or what is it?。