链表反转不开辟新空间

看了很多都不全面，这里贴一个自己测试的完整例子，亲测有效

#include <iostream>

using namespace std;

struct ListNode
{
	int value;
	ListNode * next;
};

ListNode * reverse(ListNode * list)
{
	if(list == NULL) 
	{
		return NULL;
	}

	ListNode* pReversedHead = NULL;
	ListNode* pNode = list;
	ListNode* pPrev = NULL;
	while(pNode != NULL)
	{
		// get the next node, and save it at pNext
		ListNode* pNext = pNode->next;
		
		// if the next node is null, the currect is the end of original 
		// list, and it's the head of the reversed list
		if(pNext == NULL)
		{
			pReversedHead = pNode;
		}
		
		// reverse the linkage between nodes
		pNode->next = pPrev;
		
		// move forward on the the list
		pPrev = pNode;
		pNode = pNext;
	}

	return pReversedHead;
}

int main()
{
	ListNode * p0 = new ListNode;
	p0->value = 1;
	//p0->next = NULL;
	
	ListNode * p1 = new ListNode;
	p1->value = 2;
	p0->next = p1;
	//p1->next = NULL;

	ListNode * p2 = new ListNode;
	p2->value = 3;
	p1->next = p2;

	ListNode * p3 = new ListNode;
	p3->value = 4;
	p2->next = p3;

	p3->next = NULL;
	
	ListNode * local = p0;
	while(local!=NULL)
	{
		cout << local->value << endl;
		local = local->next;
	}

	//链表反转 
	ListNode * p4 = reverse(p0);
	
	cout << "--------" << endl;
	
	while(p4!=NULL)
	{
		cout << p4->value << endl;
		p4 = p4->next;
	}
	
	return 0;
}