C ++双指针分配

Question

以下两种分配方法之间是否有区别？

int * ptr1;
int ** ptr2;

//method 1
*ptr2 = ptr1;
//method 2
ptr2 = &ptr1;

Answer 1

int* ptr; //declare a pointer
int** ptr2; //declare a pointer that will point to another pointer

*ptr2 = ptr; //dereferencing invalid address, undefined behaviour
ptr2 = &ptr; //makes ptr2 point to ptr

他们不一样！