0024.h

#include "common.h"

namespace s0024 {
    //  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, head);
            ListNode* cur = dummyHead;
            while (cur->next != nullptr && cur->next->next != nullptr) {
                ListNode* tmp = cur->next;
                ListNode* tmp1 = cur->next->next->next;
                cur->next = cur->next->next;
                cur->next->next = tmp;
                cur->next->next->next = tmp1;
                cur = cur->next->next;
            }
            return dummyHead->next;
        }
    };
}