everystep

24. 两两交换链表中的节点

class Solution {
public:
    ListNode* swapPairs(ListNode* head) {
        // 使用哨兵节点简化头节点的交换逻辑
        ListNode* dummy = new ListNode(0);
        dummy->next = head;
        ListNode* current = dummy;

        while (current->next != nullptr && current->next->next != nullptr) {
            ListNode* first = current->next;
            ListNode* second = first->next;

            // 进行节点交换
            first->next = second->next;
            second->next = first;
            current->next = second;

            // 移动指针，准备下一对交换
            current = first;
        }

        // 保存新的头节点
        ListNode* newHead = dummy->next;
        delete dummy; // 释放哨兵节点
        return newHead;
    }
};