C++编译报错，写入内存错误

Question

//changeLength2D
#include
#include
using namespace std;
//template
void changeLength2D(int**& a, int oldrow, int copyrow, int copycoloum, int newrow, int newcoloum)
{
if (copyrow > newrow || copycoloum > newcoloum)
//throw("the array is too small");
;
int**temp = new int*[newrow];
for (int i = 0; i < newrow; i++)
temp[i] = new int [newcoloum];

for (int i = 0; i < copyrow; i++)
{
    copy(a[i], a[i] + copycoloum, temp[i]);
    delete[] a[i];
}
for (int i = copyrow; i < oldrow; i++)
    delete[] a[i];
//delete[] a;
a = temp;

}

int main() {
int a[4][4] = { { 1,2,3,4},{5,6,7,8},{9,10,11,12},{13,14,15,16} };
int **b=0;

for (int i = 0; i < 4; i++)
b[i] = &a[i][4];
changeLength2D(b, 4, 2, 2, 4, 4);
for (int i = 0; i < 4; i++)
{
for (int j = 0; j < 4; j++)
cout << a[i];
cout << endl;
}

return 0;

}

调试后报错是这样的：引发了异常: 写入访问权限冲突。
b 是 0x1110112。
我检查了好像没有内存越界，数组传参对不对？这个不是很理解的透彻！希望有人解答！谢谢额。这是个改变2维数组的函数。

Answer 1

a被delete之后，没有重新分配内存，直接赋值会出错