Application of "Leetcode" Swap Nodes in Pairs linked list pointers

Title: Swap nodes in pairs

<span style= "FONT-SIZE:18PX;" >/** * Leetcode Swap Nodes in Pairs  * Title: Enter a list of two nodes each adjacent to the linked list after the switch position output * idea: traverse once, time complexity O (n) * Definition for singly- Linked list. * public class ListNode {*     int val; *     ListNode Next; *     listnode (int x) {*         val = x; *         next = null; *< c7/>} *} */package Javatrain; public class Train12 {public ListNode swappairs (ListNode head) {if (head = = NULL | | head.next = = NULL) return null;        ListNode Pnode;        Pnode = head;        while (Pnode = null && pnode.next! = null) {        int temp;         temp = Pnode.val;        Pnode.val = PNode.next.val;        PNode.next.val = temp;        Pnode = PNode.next.next;         }        return head;    }} </span>

Application of "Leetcode" Swap Nodes in Pairs linked list pointers