C++ 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) {
        //增加一个头结点指针
        ListNode* headPtr = new ListNode(0);
        headPtr->next = head;
        // 增加一个游标
        ListNode* cur = headPtr;

        //标记前后两个要交换的节点
        ListNode* first = NULL;
        ListNode* second = NULL;

        //遍历所有节点
        while (cur->next != NULL) {
            first = cur->next;
            if (first == NULL)
                break;
            second = first->next;
            if (second == NULL)
                break;
            //交换节点
            cur->next = second;
            first->next = second->next;
            second->next = first;
            cur = first;
        }

        return headPtr->next;
    }
};