题目：

题解：

struct ListNode* swapPairs(struct ListNode* head) {
    struct ListNode dummyHead;
    dummyHead.next = head;
    struct ListNode* temp = &dummyHead;
    while (temp->next != NULL && temp->next->next != NULL) {
        struct ListNode* node1 = temp->next;
        struct ListNode* node2 = temp->next->next;
        temp->next = node2;
        node1->next = node2->next;
        node2->next = node1;
        temp = node1;
    }
    return dummyHead.next;
}