LeetCode - Remove Duplicates from Sorted List

RemoveDuplicatesfromSortedList.java

//
public ListNode deleteDuplicates(ListNode head) {
        if(head == null) return head;
        ListNode pre = head, cur = head.next;
        while(cur != null){
            if(cur.val != pre.val){
                cur = cur.next;
                pre = pre.next;
            } else {
                pre.next = cur.next;
                cur = pre.next;
            }
        }
        return head;
    }
    
//
public ListNode deleteDuplicates(ListNode head) {
        ListNode ret = head;
        if(head == null)
            return head;
        while(head.next != null){
            ListNode p1 = head.next;
            if(p1.val == head.val){
                head.next = p1.next;
            }else{
                head = head.next;
            }
        }
        return ret;
    }