题解 | #删除有序链表中重复的元素-II#

/*
 * function ListNode(x){
 *   this.val = x;
 *   this.next = null;
 * }
 */

/**
  * 
  * @param head ListNode类 
  * @return ListNode类
  */
function deleteDuplicates( head ) {
    if(!head) return null
    if(head.next == null) return head;
    let startNode = null;
    let temp = null;
    let thead = head;
    let res = new ListNode(0);
   head.last = res;
    res.next = head;
    while(thead){
        if(thead.next && thead.next.val == thead.val){
                
            if(startNode == null){
                startNode = thead.last;
            }
             thead = thead.next;
        }else{
            if(startNode != null){
                startNode.next = thead.next;
                thead =  thead.next;
                if(thead){
                  thead.last = startNode;}
              
                startNode = null;
            }else{
            temp = thead;
            thead = thead.next;
            if(thead){
                 thead.last = temp;
            }
           
            }
            
        }
    }
    return  res.next
}
module.exports = {
    deleteDuplicates : deleteDuplicates
};