[数据结构与算法]力扣 C++ 链表结点两两交换

#include<iostream>
using namespace std;
typedef struct node
{
	int data;
	node* next;
};
class List
{
private:
	node* head;
	node* last;
public:
	List()//initialize linked list(初始化链表)
	{
		head = new node;
		head->next = NULL;
		last = head;
	}
	void CreateList(int a[], int length)
	{
		for (int i = 0; i < length; ++i)
		{
			node* temp = new node;
			temp->data = a[i];
			last->next = temp;
			last = temp;
		}
		last->next = NULL;
	}
	void DisplayList()
	{
		if (head->next == NULL)
			return;
		for (node* p = head->next; p; p = p->next)
			cout << p->data << '\t';
		cout << endl;
	}
	void Swap()
	{
		if (head->next == NULL || head->next->next == NULL)
			return;
		//set the two pointer p and q to point to the front and the back node of the data field respectively,and then make the next node of the head node point to null
		//设置p，q两个指针分别指向数据域的前后两个结点，再令头结点的下一个结点指向空
		node* p = head->next;
		node* q;
		head->next = NULL;
		node *last = head;
		while (p)
		{
			q = p->next;
			//when it is odd,the last node is directly connected
			//当为奇数时，直接连接最后一个结点
			if (q == NULL)
			{
				last->next = p;
				last = p;
				last->next = NULL;
				return;
			}
			last->next = q;
			last = q;
			//at this time ,the first node address of the node to be exchanged must be recorded,otherwise the address will be lost
			//此时一定要记录下一个要交换结点的首结地址不然地址丢失
			node* temp;
			 temp=q->next;
			last->next = p;
			last = p;
			last->next = NULL;
			p = temp;
		}
		
	}
};
int main()
{
	int a[6] = { 1,2,3,4,5,6};
	List list;
	list.CreateList(a, 6);
	cout << "链表未交换结点前结果" << endl;
	list.DisplayList();
	cout << "链表交换结点后结果" << endl;
	list.Swap();
	list.DisplayList();
}

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