83. 移除已排序链表中重复的节点 Remove Duplicates from Sorted List

public class Solution {
    public ListNode DeleteDuplicates(ListNode head) {
        if (head == null)
        {
            return null;
        }
        ListNode node = head;
        ListNode nextNode = null;
        while (node.next != null)
        {
            if (node.val == node.next.val)
            {
                nextNode = node.next;
                while (nextNode.val == node.val)
                {
                    if (nextNode.next == null)
                    {
                        node.next = null;
                        return head;
                    }
                    else
                    {
                        nextNode = nextNode.next;
                    }
                }
                node.next = nextNode;
                node = nextNode;
            }
            else
            {
                node = node.next;
            }
        }
        return head;
    }
}

public class Solution {
        if (head == null) return head;
        ListNode node = head;
        while (node.next != null)
        {
            if (node.val == node.next.val)
            {
                node.next = node.next.next;
            }
            else
            {
                node = node.next;
            }
        }
        return head;
    }
}