leetcode-206. 反转链表

 

 

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
class Solution {
public:
    ListNode* reverseList(ListNode* head) {
        if(head==NULL)
            return NULL;
        ListNode* L = NULL;  // 定义尾指针
        while(head){
            ListNode* temp = head->next;
            head->next = L;
            L = head;
            head = temp;
        }
        return L;
    }
};