为什么我不能从链表中删除重复项？

您正在删除重复的节点,而不是您发布的代码中的重复节点.

 /*
DEFINITIONS

public class ListNode {
    int val;
    ListNode next;
    public ListNode(int x){
        val = x;
        next = null;
    }

}


public class LinkedList {
    ListNode head;
}
*/


public void removeDups(){
    ListNode head = this.head;
    if(head == null) return;

    HashSet set = new HashSet();
    set.add(head.val);
    while(head.next != null){
        if(set.contains(head.next.val)){
            head.next = head.next.next;
        } else{
            set.add(head.next.val);
            head = head.next;
        }
    }
}