c++ - 在 C++ 中如何修复我的程序崩溃？

Question

我是编程新手，我正在尝试编写一个对多项式进行加减运算的程序。我的程序有时可以运行，但大多数时候，它随机崩溃，我不知道为什么。它有很多错误，还有其他我正在尝试修复的问题，但由于它崩溃，我无法真正完成任何进一步的编码。我在这里是全新的，但我们将不胜感激任何帮助。

代码如下:

#include <iostream>
#include <cstdlib>

using namespace std;

int getChoice();
class Polynomial10
{
private:
    double* coef;
    int degreePoly;

public:
    Polynomial10(int max); //Constructor for a new Polynomial10
    int getDegree(){return degreePoly;};
    void print(); //Print the polynomial in standard form
    void read(); //Read a polynomial from the user
    void add(const Polynomial10& pol); //Add a polynomial
    void multc(double factor); //Multiply the poly by scalar
    void subtract(const Polynomial10& pol); //Subtract polynom
};

void Polynomial10::read()
{
    cout << "Enter degree of a polynom between 1 and 10 : ";
    cin >> degreePoly;

    cout << "Enter space separated coefficients starting from highest degree" << endl;
    for (int i = 0; i <= degreePoly; i++) cin >> coef[i];
}

void Polynomial10::print()
{
    for (int i = 0;i <= degreePoly; i++) {
       if (coef[i] == 0) cout << "";
       else if (i >= 0) {
           if (coef[i] > 0 && i != 0) cout<<"+";
           if ((coef[i] != 1 && coef[i] != -1) || i == degreePoly) cout << coef[i];
           if ((coef[i] != 1 && coef[i] != -1) && i != degreePoly ) cout << "*";
           if (i != degreePoly && coef[i] == -1) cout << "-";
           if (i != degreePoly) cout << "x";
           if ((degreePoly - i) != 1 && i != degreePoly) {
               cout << "^";
               cout << degreePoly-i;
           }
       }
   }
}

void Polynomial10::add(const Polynomial10& pol)
{
    for(int i = 0; i<degreePoly; i++) {
        int degree = degreePoly;
        coef[degreePoly-i] += pol.coef[degreePoly-(i+1)];
    }
}

void Polynomial10::subtract(const Polynomial10& pol)
{
    for(int i = 0; i<degreePoly; i++) {
        coef[degreePoly-i] -= pol.coef[degreePoly-(i+1)];
    }
}

void Polynomial10::multc(double factor)
{
    //int degreePoly=0;
    //double coef[degreePoly];
    cout << "Enter the scalar multiplier : ";
    cin >> factor;
    for(int i = 0; i<degreePoly; i++) coef[i] *= factor;
}

Polynomial10::Polynomial10(int max)
{
    degreePoly = max;
    coef = new double[degreePoly];
    for(int i; i < degreePoly; i++) coef[i] = 0;
}

int main()
{
    int choice;
    Polynomial10 p1(1),p2(1);
    cout << endl << "CGS 2421: The Polynomial10 Class" << endl << endl << endl;
    cout
        << "0. Quit\n"
        << "1. Enter polynomial\n"
        << "2. Print polynomial\n"
        << "3. Add another polynomial\n"
        << "4. Subtract another polynomial\n"
        << "5. Multiply by scalar\n\n";

    int choiceFirst = getChoice();
    if (choiceFirst != 1) {
        cout << "Enter a Polynomial first!";
    }
    if (choiceFirst == 1) {choiceFirst = choice;}

    while(choice != 0) {
        switch(choice) {
            case 0:
                return 0;
            case 1:
                p1.read();
                break;
            case 2:
                p1.print();
                break;
            case 3:
                p2.read();
                p1.add(p2);
                cout << "Updated Polynomial: ";
                p1.print();
                break;
            case 4:
                p2.read();
                p1.subtract(p2);
                cout << "Updated Polynomial: ";
                p1.print();
                break;
            case 5:
                p1.multc(10);
                cout << "Updated Polynomial: ";
                p1.print();
                break;
        }
        choice = getChoice();
    }
    return 0;
}

int getChoice()
{
    int c;
    cout << "\nEnter your choice : ";
    cin >> c;
    return c;
}

Answer 1

当您使用 p1(1) 和 p2(1) 创建对象时，每个对象中的 coef 数组被分配为包含一个元素。然后在 read() 中，您只需将 degreePoly 设置为一个(可能更高的)值，但不要更改 coef 的分配。它仍然只包含一个元素，但所有系数都写入其中，可能会超出数组的边界。相反，应该释放旧的 coef 并分配一个合适大小的新数组。

此外，在 add 和 subtract 中，您分配给超出范围的系数(对于 i=0):

coef[degreePoly-i] -= pol.coef[degreePoly-(i+1)];

从索引 degreePoly-i 的系数中减去索引 degreePoly-(i+1) 的系数在数学上似乎也是错误的。此外，目前还没有处理两个多边形可能具有不同度数的情况。