Delete duplicate nodes in a linked list

The topic is described in a sorted list, where there are duplicate nodes, delete the duplicate nodes in the linked list, duplicate nodes are not retained, and return the chain header pointers. For example, the list 1->2->3->3->4->4->5 is treated as 1->2->5Public class Solution {Public ListNode deleteduplication (listnode phead){ListNode first = new ListNode (-1);//Set up a predecessor node for the head junction .first.next = phead;ListNode p = phead;ListNode last = first;//assign this predecessor node toWhile (P! = null && P.next = null) {if (p.val = = p.next.val) {int val = p.val;While (P! = null && val = = p.val)p = p.next;//If the values of the current and next nodes are the same, p continues to move backwardslast.next = p;             }else {Last = P;p = p.next;            }        }return first.next;    }}

Delete duplicate nodes in a linked list