在用C 2D动态存储器分配阵列自由分配的内存++(free allocated memory in

我最近发布了关于这个问题，但是这是一个不同的问题。我创建使用动态内存分配的二维数组，使用矩阵后，我们需要释放被删除的记忆，我不明白为什么我们不能只是使用delete [] matrix在下面代码删除它，而不是方法

int **matrix;

    // dynamically allocate an array
    matrix = new int *[row]; 
    for (int count = 0; count < row; count++)
        matrix[count] = new int[col];

    // free dynamically allocated memory
    for( int i = 0 ; i < *row ; i++ )
    {
        delete [] matrix[i] ;
        delete [] matrix ;
    }

因为这个问题是因为在main()我创建一个二维数组，并使用其他分配值int **功能，我不知道如何删除所分配的存储器，环路会引起运行时错误

    int main()
    {
        int **matrixA = 0, **matrixB = 0, **matrixResult = 0; // dynamically allocate an array
        int rowA, colA, rowB, colB; // to hold the sizes of the matrices

        // get values for input method
        int inputMethod = userChoiceOfInput();
        if (inputMethod == 1) // select input by keyboard
        {
            cout << "Matrix A inputting...\n";
            matrixA = getMatricesByKeyboard(&rowA, &colA);
            cout << "Matrix B inputting...\n";
            matrixB = getMatricesByKeyboard(&rowB, &colB);
        }
        else if (inputMethod == 2) // select input by files
        {
            matrixA = getMatricesByFileInput("F:\\matrixA.txt", &rowA, &colA); 
            matrixB = getMatricesByFileInput("F:\\matrixB.txt", &rowB, &colB); 
        }

        //addition(matrixA, &rowA, &colA, matrixB, &rowB, &colB);

        cout << matrixA[1][0];  

////////////////////////run time error///////////////////////
    // free allocated memory of matrix A
    for( int i = 0 ; i < rowA ; i++ )
    {
        delete [] matrixA[i] ;
        delete [] matrixA ;
    }
    // free allocated memory of matrix B
    for( int i = 0 ; i < rowB ; i++ )
    {
        delete [] matrixB[i] ;
        delete [] matrixB ;
    }
////////////////////////run time error///////////////////////

        // free allocated memory of matrix A
        delete [] matrixA ; // i dont know what would these delete
        delete [] matrixB ; 

        return 0;
    }

Answer 1:

你必须通过你的矩阵，并删除每个阵列。在这样做，你可以删除矩阵本身的结束

// free dynamically allocated memory
for( int i = 0 ; i < *row ; i++ )
{
    delete[] matrix[i]; // delete array within matrix
}
// delete actual matrix
delete[] matrix;

Answer 2:

如果使用的是动态数组反正我会强烈建议使用std :: vector的。该性能损失是微乎其微，并考虑可以更加妥善地使用std算法与向量代码很可能最终更好的性能。

unsigned int cols=40, rows=35;
std::vector<int> temp(cols,0); //this is only created so that we can initialize a 
                               //row at a time, the first parameter is the amount of 
                               //elements to initialize with and the second is the value
                               //to initialize with
std::vector<std::vector<int>> matrix(rows,temp); //creates a vector with 35 vectors each
                                                 //initialized with the values in temp

matrix[2][3] = 4;              //use just like a normal array
matrix.resize(88,temp);         //you can add rows later too
matrix.push_back(temp);         //or like this

//probably the most important, you don't need to delete because you never needed to 
//use new in the first place

使用new和delete是不是真的现代风格，有很好的理由。据在C ++和超越惯例，应该只有在性能优化的情况下编写库代码时使用和大师。许多书籍和老师还在教这种方式，但另一方面大多数书籍都是垃圾。下面是其中的宝石：权威C ++书指南和列表

Answer 3:

由于类型为int *没有desctructor，至少它有你所要的析构函数。你可以避开所有的内存分配/释放的东西做这样的事情

std::vector<int*> matrix(rows);
std::vector<int> allData(rows * cols);
for(int i = 0; i < rows; i++)
{
matrix[i] = &allData[i * cols];
}

或通过使用类似的boost ::数字:: uBLAS库::矩阵标准容器。

文章来源: free allocated memory in 2D dynamic memory allocation array in C++