优选算法_翻转链表_头插法_C++

一.题目解析

算法解析:

结合画图和头插代码就很好理解了

二.代码编写:

/**
 * 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||head->next==nullptr)return head;

        ListNode*newhead=new ListNode(0);
        ListNode*cur=head;
        while(cur!=nullptr)
        {
            ListNode*next=cur->next;//注意顺序和位置
            cur->next=newhead->next;
            newhead->next=cur;
            cur=next;
        }
        cur=newhead->next;
        delete newhead;
        return cur;
    }
};