Linked list: reverse linked list

subject

https://leetcode-cn.com/problems/UHnkqh/

Their thinking

Reverse the linked list , You can use double pointers pre and cur To solve .
It should be noted that ：

1. pre Pointer to null node ,cur Point to the head node .
2. In exchange for pre and cur When you're pointing , Temporary storage required cur Of next node .
   During backward traversal of the pointer , In exchange for cur.next = pre. So as to complete the inversion of the linked list . The specific steps are as follows ：

Code

/** * Definition for singly-linked list. * public class ListNode { * int val; * ListNode next; * ListNode() {} * ListNode(int val) { this.val = val; } * ListNode(int val, ListNode next) { this.val = val; this.next = next; } * } */
class Solution {
    
    public ListNode reverseList(ListNode head) {
    
        ListNode pre = null;
        ListNode cur = head;
        while(cur != null) {
    
            ListNode temp = cur.next;
            cur.next = pre;
            pre = cur;
            cur = temp;
        }
        return pre;
    }
}

summary

Reverse a linked list , It mainly focuses on how to exchange the pointers of two linked lists , At the same time, cache the next node first , To continue traversing the linked list . This problem can be solved with double pointers .