leetcode-----24. 两两交换链表中的节点

• 链接：https://leetcode-cn.com/problems/swap-nodes-in-pairs/

代码

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode* swapPairs(ListNode* head) {
        auto dummy = new ListNode(-1);
        dummy->next = head;
        for (auto p = dummy; p->next && p->next->next;) {
            auto a = p->next, b = a->next;
            p->next = b;
            a->next = b->next;
            b->next = a;
            p = a;
        }
        return dummy->next;
    }
};