LeetCode || Reverse Linked List

来源：互联网发布：macbook视频剪辑软件编辑：程序博客网时间：2024/05/19 19:16

写法一：非递归实现。

/** * Definition for singly-linked list. * struct ListNode { *     int val; *     ListNode *next; *     ListNode(int x) : val(x), next(NULL) {} * }; */class Solution {public:    ListNode* reverseList(ListNode* head) {        if(head == NULL)            return NULL;        ListNode * t = head;                head = head->next;        t->next = NULL;        ListNode* tNext = t;        while(head != NULL)        {            t = head;             head = head->next;            t->next = tNext;            tNext = t;        }                return t;    }};

写法2：递归实现。

/** * Definition for singly-linked list. * struct ListNode { *     int val; *     ListNode *next; *     ListNode(int x) : val(x), next(NULL) {} * }; */class Solution {public:    ListNode* reverseList(ListNode* head) {        if(head == NULL || head->next == NULL)            return head;                ListNode* pNewHead = head;        while(pNewHead->next!=NULL)            pNewHead = pNewHead->next;        reverse(head);        return pNewHead;    }        ListNode* reverse(ListNode* head)    {        if(head->next == NULL)            return head;        else        {            ListNode* tail = reverse(head->next);            tail->next = head;            tail = tail->next;            tail->next = NULL;            return tail;        }    }};

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