单链表逆序 也叫反转

I have browsed many codes about the list reversed, most of which are hard to understand and complicated;

to reverse a single list, two methods can be required:

1; create a another list from the old list reversed, that is to say the new nodes are coming from the tail of the old list.

2; reverse the pointer; we need only to reverse the pointer from next to prior;

so we found the last method are better than first , because it is terse and without allocating new memory;

for example, original order is following:

prior      cur         next

○->○->○

reverse

○<-○<-○

ok, principle is easy to understand, implement it

#include
using namespace std;

struct Node
{
	int data;
	struct Node *next;
};

struct Node *createList(const int & aiNum)
{
	struct Node *head = NULL;
	struct Node *newPtr = NULL;
	struct Node *cur;
	int i = 0;
	for (; i < aiNum; i++ )
	{
		if (!head)
		{
			head = (struct Node*)malloc(sizeof(Node));
			head->data = i;
			head->next = NULL;

			cur = head;
		}
		else
		{
			newPtr = (struct Node*)malloc(sizeof(Node));
			newPtr->data = i;
			newPtr->next = NULL;
			cur->next = newPtr;
	    	cur = cur->next;
		}
	}
	cur->next = NULL;

	return head;
}

void printNode(struct Node * head)
{
	cout<<"print node"<<endl;
	struct Node * lptr = head;
	while (lptr)
	{
		cout<<lptr->data<<endl;
		lptr = lptr->next;
	}
}

void destroyList(struct Node * head)
{
	cout<<"destroy list"<<endl;
	struct Node *cur = head;
	int i = 0;
	while (head)
	{
		cur = head;
		cout<<cur->data<<endl;
		head = head->next;
		free(cur);
	}
}

Node* reverseList(struct Node * head)
{
	Node *prior = head;
	Node * cur = prior->next;
	Node * next = NULL;

	while (cur->next)//prior->cur->next
	{
		next = cur->next;
		cur->next = prior;//prior<-cur->next
		prior = cur;      //      prior cur  ;move to the next node for next loop
		cur = next;
	}
	head->next = NULL;   //set the tail as NULL
	cur->next = prior;  //the last loop , since the cur->next is null , 
	                  //the pointer is still from head to cur,so we must reverse it additional
	printNode(cur);

	return cur;
}
void main()
{
	struct Node *head = createList(5);
	printNode(head);
	struct Node *rhead = reverseList(head);

	destroyList(rhead);
}