206. Reverse Linked List

题目

Reverse a singly linked list.

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思路

两个指针一前一后遍历翻转链表指向，注意最后要把最开始的head的next指针弄成NULL

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代码

/** * 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* preNode = head;        ListNode* laterNode = head->next;        ListNode* tempNode = NULL;        while(laterNode != NULL)        {            tempNode = laterNode->next;            laterNode->next = preNode;            preNode = laterNode;            laterNode = tempNode;        }        //最后一定要把反转后的最后一个节点next置NULL        head->next = NULL;        return preNode;    }};