LertCode - 83. 删除排序链表中的重复元素

import java.util.Objects;

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

class Solution {

public ListNode deleteDuplicates(ListNode head) {

if (Objects.isNull(head)) {
return null;
}

ListNode p = head.next;
ListNode pre = head;

while (Objects.nonNull(p)) {
if (p.val == pre.val) {
pre.next = p.next;
p.next = null;
p = pre.next;
} else {
pre = p;
p = p.next;
}

}
return head;
}
}