循环链表(4) - 分割链表为两段

#include <iostream>

//链表节点
struct Node
{
	int data;
	Node *next;
};

//将一个链表(head)分割为两个链表。head1和head2分别代表分割后的两个链表。
void splitList(Node *head, Node **head1, Node **head2)
{
	Node *slowPtr = head;
	Node *fastPtr = head;

	if (head == NULL)
		return;

	//如果循环链表节点个数为奇数，则最终fastPtr->next会与head重合
	//如果个数为偶数，则fastPtr->next->next会与head重合
	while (fastPtr->next != head &&
		fastPtr->next->next != head)
	{
		fastPtr = fastPtr->next->next;
		slowPtr = slowPtr->next;
	}

	//如果有偶数个节点，则移动fastPtr
	if (fastPtr->next->next == head)
		fastPtr = fastPtr->next;

	//设置前半部分的头指针
	*head1 = head;

	//设置后半部分的头指针
	if (head->next != head)
		*head2 = slowPtr->next;

	//使后半部分形成循环链表
	fastPtr->next = slowPtr->next;

	//使前半部分形成循环链表
	slowPtr->next = head;
}

//在循环链表头部插入新的节点
void push(Node **head, int data)
{
	Node *newNode = new Node;
	Node *temp = *head;
	newNode->data = data;
	newNode->next = *head;

	//如果链表不为空，则将最后一个节点的后向指针设置为新节点
	//即新节点变成了新的头节点。
	if (*head != NULL)
	{
		while (temp->next != *head)
			temp = temp->next;
		temp->next = newNode;
	}
	else
		newNode->next = newNode; //新节点做为链表第一个节点

	*head = newNode;  //调整头节点
}

//打印循环链表
void printList(Node *head)
{
	Node *temp = head;
	if (head != NULL)
	{
		do
		{
			std::cout << " " << temp->data << " ";
			temp = temp->next;
		} while (temp != head);
	}
}

int main()
{
	//初始化链表为：1->2->3->4->5->6->7
	Node *head = NULL;
	Node *head1 = NULL;
	Node *head2 = NULL;

	push(&head, 7);
	push(&head, 6);
	push(&head, 5);
	push(&head, 4);
	push(&head, 3);
	push(&head, 2);
	push(&head, 1);

	std::cout << "Original Circular Linked List \n";
	printList(head);
	std::cout << std::endl;

	//分割链表
	splitList(head, &head1, &head2);

	std::cout << "\nFirst Circular Linked List \n";
	printList(head1);
	std::cout << std::endl;

	std::cout << "\nSecond Circular Linked List \n";
	printList(head2);
	std::cout << std::endl;

	return 0;
}