206. Reverse Linked List

Reverse a singly linked list.

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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)        return head;        ListNode* pre=NULL;        while( head )        {            ListNode* temp=head->next;            head->next = pre;            pre= head;            head = temp;        }        return pre;    }};