单链表反转

单链表反转：这个是反转是要破坏原有数据结构的。

算法1：红色线为将要修改节点的指向，这里只要关注几个节点：Head->next，Cur，Cur->next，Cur->next->next，遍历整个链表调整即可。

 

#include <iostream>

using namespace std;

typedef struct _Node
{
	struct _Node*	next;
	int		num;
} Node;

Node* reverse_list(Node* head)
{
	Node* cur = NULL;
	Node* tmp = NULL;
	Node* last = NULL;

	if (NULL != head && NULL != head->next)
	{
		cur = head->next;
		while (cur != NULL && cur->next != NULL)
		{
			tmp = cur->next;
			last = tmp->next;

			cur->next = tmp->next;
			tmp->next = head->next;
			head->next = tmp;
		}
	}
	return head;
}

int main()
{
	Node* head = new Node;

	Node* node1 = new Node;
	node1->num = 1;
	head->next = node1;

	Node* node2 = new Node;
	node2->num = 2;
	node1->next = node2;

	Node* node3 = new Node;
	node3->num = 3;
	node2->next = node3;

	Node* node4 = new Node;
	node4->num = 4;
	node3->next = node4;

	Node* node5 = new Node;
	node5->num = 5;
	node4->next = node5;
	node5->next = NULL;

	head = reverse_list(head);

	Node* tmp = head->next;
	while (tmp != NULL)
	{
		cout<<tmp->num<<endl;
		tmp = tmp->next;
	}

	return 0;
}

算法2：用递归

Node* reverse_list(Node* head)
{
	if (head->next == NULL)
	{
		return head;
	}

	Node* tmp = reverse_list(head->next);
	head->next->next = head;
	head->next = NULL;

	return tmp;
}