LeetCode每日一题【24. 两两交换链表中的节点】

思路：先创建虚拟头结点，再用双指针，两两交换

/*** Definition for singly-linked list.* struct ListNode {*     int val;*     ListNode *next;*     ListNode() : val(0), next(nullptr) {}*     ListNode(int x) : val(x), next(nullptr) {}*     ListNode(int x, ListNode *next) : val(x), next(next) {}* };*/
class Solution {
public:ListNode* swapPairs(ListNode* head) {ListNode* dummyHead = new ListNode(0);dummyHead->next = head;ListNode* cur = dummyHead;while(cur->next && cur->next->next){ListNode* temp1 = cur->next;ListNode* temp2 = cur->next->next->next;cur->next = cur->next->next;cur->next->next = temp1;cur->next->next->next = temp2;cur = cur->next->next;}return dummyHead->next;}
};