Question

因此，对于作业，我必须创建一个程序，当用户输入一个奇数时会创建魔术方块，我已完成大部分程序但由于某些原因当我尝试填充方块时，我得到0x00326315处的未处理异常在magic square.exe中：0xC0000005：访问冲突读取位置0x00000000

我使用类并将square的声明作为int ** square;

这是代码

#include<iostream>
#include<iomanip>
#include"MagicSquare.h"

using namespace std;

MagicSquare::MagicSquare(): size(0), maxNum(0), row(0), col(0), curNum(0) //Constructor initialize variables
{
}

MagicSquare::~MagicSquare()                             //Destructor 
{
for (int i = 0; i < size; i++)
{
    delete[] square[i];
}
delete[] square;                                                                            //Delete the dynamically allocated memory
}
void MagicSquare::getSize() //Get the size of the magic square
{
    cout << "Please enter an odd number for the number of rows/columns: ";
    cin >> size;
    while (size % 2 == 0) //Check to see if the number entered is odd
    {
        cout << "The number you entered is not odd, please enter an odd number: ";
        cin >> size;
    }

    int **square = new (nothrow) int*[size];
    for (int i = 0; i < size; i++)
    {
        square[i] = new (nothrow) int[size];
    }
    maxNum = size * size;
    iCount = new (nothrow) int[size];
    jCount = new (nothrow) int[size];
}

void MagicSquare::populateSquare()
{
    for (int i = 0; i < size; i++)
    {
        for (int j = 0; j < size; j++)
        {
            square[i][j] = 0;     //This is where the error occurs
        }
    }
    curNum = 1;
    col = (size - 1) / 2;
    square[row][col] = curNum;
    curNum += 1;
    for (int i = 1; i <= maxNum; i++)
    {
        row = row - 1;
        col = col + 1;
        if (col >= size)
            col = 0;
        if (row < 0)
            row = size - 1;
        square[row][col] = curNum;
        curNum += 1;
    }
}

标头文件

class MagicSquare
{
private:
int **square;
int size;
int maxNum;
int row;
int col;
int curNum;
int *iCount;
int *jCount;

public:
MagicSquare();
~MagicSquare();
void getSize();
void populateSquare();
void printSquare();
};

源文件

#include"MagicSquare.h"
#include<iostream>


using namespace std;


int main() 
{
MagicSquare mySquare;

int choice = 1;
while (choice == 1)
{
    mySquare.getSize();
    mySquare.populateSquare();
    mySquare.printSquare();

    cout << "\n\nWould you like to create another magic square? 1 for yes, 0 for no: ";
    cin >> choice;
    while (choice != 1 || choice != 0)
    {
        cout << "\nInvalid input: \nWould you like to create another magic square? 1 for yes, 0 for no: ";
        cin >> choice;
    }
}

system("pause");

return 0;
}

Answer 1

您在square方法中定义了一个名为getSize()的局部变量：

int **square = new (nothrow) int*[size];。

所以你为局部变量留出空间，但从不为类的字段留出空间。

将此行更改为

square = new (nothrow) int*[size];

还要认真考虑检查通话结果。

Answer 2

访问冲突读取位置0x00000000告诉您，您正在尝试访问NULL指针。原因可能是，new的至少一次调用失败了。你应该在分配数组时检查：

int **square = new (nothrow) int*[size];
if(square == NULL)
    //Handle error here
for (int i = 0; i < size; i++)
{
    square[i] = new (nothrow) int[size];
    if(square == NULL)
        //Handle error here
}

但我猜这不是原因。如果我看到它，你有两个功能：

void MagicSquare::getSize() 
void MagicSquare::populateSquare()

但是int **square是在getSize中创建的，所以如果你调用populate square，这个变量就不再存在了。

如果你的班级是：

class MagicSquare
{
private:
    int **square;
public:
    //Methods
}

在getSize中，您必须将地址存储在classes成员变量中，而不是您刚刚创建的本地变量：

square = new (nothrow) int*[size]; //without int **

使用指针创建2d动态数组

2 个答案: