【leetcode】反转链表-25-2

fighting的码农(zg)-GPT2024-08-21 18:45

方法：遍历

cpp 复制代码

/**
 * 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* A=nullptr;
        ListNode* B=nullptr;
        while(head!=nullptr){
            B=head;
            head=head->next;
            B->next=A;
            A=B;
        }
        head=B;
        return head;

    }
};

方法：递归

cpp 复制代码

/**
 * 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* recurveReverseList(ListNode* A,ListNode* B){
        if(B->next==nullptr){
            B->next=A;
            return B;
        }
        ListNode* T=B;
        B=B->next;
        T->next=A;
        A=T;
        return recurveReverseList(A,B);
    }
    ListNode* reverseList(ListNode* head) {
        if(head==nullptr){
            return head;
        }
        return recurveReverseList(nullptr,head);
    }
};