【C++】如何删除指针（链表节点）

由于在进行链表操作时，尤其是删除节点时，经常会因为对当前节点进行操作而导致内存或
指针出现问题。有两个小技巧可以解决这个问题：一是尽量处理当前节点的下一个节点而非当前
节点本身，二是建立一个虚拟节点 (dummy node)，使其指向当前链表的头节点，这样即使原链表
所有节点全被删除，也会有一个 dummy 存在，返回 dummy->next 即可。

删除链表中的某个节点可以这样写：

delete pToBeDeleted;
pToBeDeleted = nullptr;

但是这两句是不可以交换的。stackoverflow中一个说明很形象：

pointer = nullptr; is like removing the ink from a business card. You no longer know where the house is located, at least not from looking at that particular business card. But the house is still there.

delete pointer; is like tearing down the house. The business card still tells you where that house used to be, but if you were to drive there (dereference the pointer), you would see the house was gone. Or worse, maybe they put up a nuclear waste storage facility at that address in the meantime.

所以上面两句代码的顺序也不可变，不然就会形成某个节点（指针指向的对象）丢失在内存中找不到，delete也删除不了。

https://stackoverflow.com/questions/31618975/whats-the-difference-between-delete-ing-a-pointer-and-setting-it-to-nullptr