题解 | #删除有序链表中重复的元素-II#

/*
 * public class ListNode {
 *   int val;
 *   ListNode next = null;
 * }
 */

public class Solution {
    /**
     * 
     * @param head ListNode类 
     * @return ListNode类
     */
    public ListNode deleteDuplicates (ListNode head) {
        // write code here
        if(head == null || head.next == null){
            return head;
        }
        ListNode newHead = new ListNode(-1);
        newHead.next = head;
        ListNode currentNode = head;
        ListNode pre = newHead;
//         int count = 0;
//         while(currentNode != null && currentNode.next != null){
//                if(currentNode.val == currentNode.next.val){
//                    count ++;
//                    currentNode.next = currentNode.next.next;
//                }else{
//                    if(count >0){
//                        pre.next = currentNode.next;
//                        count = 0;
//                    }else{
//                        pre = currentNode;
//                    }
//                    currentNode = currentNode.next;
//                }
             
            
//         }
//         if(count > 0){
//             pre.next = currentNode.next;
//         }
        while(currentNode != null){
            ListNode next = currentNode.next;
            boolean needDel = false;
            if(next != null && currentNode.val == next.val){
                needDel = true;
            }
            if(!needDel){
                pre = currentNode;
                currentNode = currentNode.next;
            }else{
                int value = currentNode.val;
                ListNode toBeDel = currentNode;
                while(toBeDel != null && toBeDel.val == value){
                    next = toBeDel.next;
                    pre.next = next;
                    toBeDel = next;
                }
                currentNode = pre.next;
            }
        }
        return newHead.next;
    }
}