代码随想录：两两交换链表中的节点

代码随想录：两两交换链表中的节点

链表题目务必用虚头节点，很多问题会变简单很多

/*** 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* virt = new ListNode;virt->next = head;ListNode* target = head;ListNode* tail = virt;while (target != NULL && target->next != NULL) {tail->next = target->next;ListNode* n = target->next->next;ListNode* node2 = target->next;target->next = n;node2->next = target;tail = target;target = n;}return virt->next;}
};