Leetcode 206. Reverse Linked List

最新推荐文章于 2024-11-04 16:11:14 发布

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本文深入探讨了链表数据结构的反转算法，提供了迭代和递归两种实现方式，并附带详细的代码示例。通过本文，读者可以理解链表反转的基本原理和具体实现步骤。

文章作者：Tyan
博客：noahsnail.com | 优快云 | 简书

1. Description

Reverse Linked List

2. Solution

Iteratively

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

Recursively

/**
 * 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) {
        return reverse(head, nullptr);        
    }
    
private:
    ListNode* reverse(ListNode* current, ListNode* pre) {
        if(!current) {
            return nullptr;
        }
        ListNode* next = current->next;
        if(next) {
            current->next = pre;
            return reverse(next, current);
        }
        current->next = pre;
        return current;
    }
    
};