leetcode之鏈表-單鏈表反轉-C++

標籤：leetcode   鏈表-單鏈表反轉   c++   

ReverseLinked List

A linked list can be reversed eitheriteratively or recursively. Could you implement both? 迭代版本：

1./** 2. * Definition for singly-linked list. 3. * struct ListNode { 4. *     int val; 5. *     ListNode *next; 6. *     ListNode(int x) : val(x), next(NULL) {} 7. * }; 8. */  9.class Solution {  10.public:  11.    ListNode* reverseList(ListNode* head) {  12.        ListNode *p;  13.        ListNode *q;  14.        ListNode *r;  15.          16.        if(head == NULL || head->next == NULL)  17.        {  18.            return head;  19.        }  20.        else  21.        {  22.            p = head;  23.            q = head->next;  24.            head->next = NULL;  25.              26.            while(q)  27.            {  28.                r = q->next;  29.                q->next = p;  30.                p = q;  31.                q = r;  32.            }  33.            head = p;  34.        }  35.        return head;  36.    }  37.};  

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leetcode之鏈表-單鏈表反轉-C++