反转链表 循环倒着建链表 - lifengyu360/lifengyu_first_git_test GitHub Wiki

/**

• 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 == nullptr){
        return head;
    }
    
    ListNode *new_head = head;
    ListNode *tail = head->next;
    new_head->next = nullptr;

    while (tail){
        ListNode *tmp = tail->next;
        tail->next  = new_head;
        new_head =  tail;
        tail = tmp;
    }

    return new_head;
}

};