LeetCode || Reverse Linked List-优快云博客

本文详细介绍了链表反转算法的两种实现方式：递归和非递归。通过具体代码实例，深入解析了每种方法的原理、步骤及应用场景，旨在为读者提供全面的理解和实践指导。

写法一：非递归实现。

/**
 * 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 NULL;
        ListNode * t = head;
        
        head = head->next;
        t->next = NULL;
        ListNode* tNext = t;
        while(head != NULL)
        {
            t = head;
             head = head->next;
            t->next = tNext;
            tNext = t;
        }
        
        return t;
    }
};

写法2：递归实现。

/**
 * 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* pNewHead = head;
        while(pNewHead->next!=NULL)
            pNewHead = pNewHead->next;
        reverse(head);
        return pNewHead;
    }
    
    ListNode* reverse(ListNode* head)
    {
        if(head->next == NULL)
            return head;
        else
        {
            ListNode* tail = reverse(head->next);
            tail->next = head;
            tail = tail->next;
            tail->next = NULL;
            return tail;
        }
    }
};