c++ 的用 new 和delete 进行二维数组动态内存的创建和删除

1.数组指针
A (*ga)
= new A[m]
;
...
delete []ga;
2.二级指针
A** ga = new A*[m];
for(int i = 0; i < m; i++)
ga[i] = new A
;
...
for(int i = 0; i < m; i++)
delete []ga[i];
delete []ga;
3.//用一维数组来模拟
A* ga = new A[m*n];
...
delete []ga;

对应的用malloc 和free 函数进行操作的方法是：
1.
int (*p)[4] = (int *[])malloc(sizeof(int) *n * m);
free(p);
2.
int **p;
for(int i = 0; i < n; i ++)
{
p[i] = (int *)malloc(sizeof(int) * m);
}
for(int i = 0; i < n; i ++)
free(p[i]);
free(p);

3.
int *p  = (int *) malloc(sizeof(int) * n *m);
free(p);