Cinte's Leetcode Record
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206. 反转链表

Posted on Edited on In Disqus:
Symbols count in article: 965 Reading time ≈ 1 mins.

206. 反转链表

迭代

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/**
 * 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) {
        ListNode* pre = nullptr;
        while(head)
        {
            auto next = head->next;
            head->next = pre;
            pre = head;
            head = next;
        }
        return pre;
    }
};

递归 

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/**
 * 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 || !head->next)
            return head;
        auto h = reverseList(head->next);
        head->next->next = head;
        head->next = nullptr;
        return h;
    }
};