C++ 在堆上开辟与释放二维、三维指针详细解析

//二维指针的开辟与释放
int **b = NULL;
b = new int*[10];
for(int i = 0; i != 10; ++i)
{
     b[i] = new int[50];
     memset(b[i], 0, sizeof(int)*50);
}

//这样就在堆上开辟了int类型的二维指针，大小为10*50，相当于在堆上一个二栈数组int b[10][50];
for(int i = 0; i != 10; ++i)
{
     delete []b[i];
     b[i] = NULL;
}
delete []b;
b = NULL;

//三维指针的开辟与释放
int ***a = NULL;
a = new int**[10];
for(int i = 0; i != 10; ++i)
{
    a[i] = new int*[50];
    for(int j = 0; j != 50; ++j)
    {
        a[i][j] = new int[30];
        memset(a[i][j], 0, sizeof(int)*30);
    }
}

//这样就在堆上开辟了int类型的三维指针，大小为10*50*30，相当于在栈上一个二维数组int a[10][50][30];
for(int i = 0; i != 10; ++i)
{
    for(int j = 0; j != 50; ++j)
    {
       delete []a[i][j];
       a[i][j] = NULL;          
    }
    delete []a[i];
    a[i] = NULL;
}
delete []a;
a = NULL;