Leetcode#24 Swap Nodes in Pairs

原题地址

 

心得：做链表类题目，多用中间变量，代码的可读性比简洁性更重要，适当注释。在纸上画画图，看看各操作节点的next指针最后都指对了没。

 

代码：

ListNode *swapPairs(ListNode *head) {
        if (!head) 
            return NULL;
        
        ListNode *prev = NULL;
        ListNode *curr = head;
        ListNode *next = curr->next;
        head = NULL;
        
        while (next) {
            ListNode *nextnext = next->next;
            if (!head)
                head = next;
            else
                prev->next = next;
            prev = next->next = curr;
            prev->next = curr = nextnext;
            next = nextnext ? nextnext->next : NULL;
        }
        
        return head ? head : curr;
}