题解 | #16.删除有序链表中重复的元素-II#

注意：

1.设置伪结点，方便处理

3.当遇到当前节点值和下一节点值相等的节点时，进行while循环找到下一个不相等的节点，挂到prev节点上

4.当遇到当前节点值和下一节点值不相等的节点时，prev和curr都移动到下一个节点接着遍历就行

function deleteDuplicates( head ) {
  if(head==null || head.next==null)
    return head;
  
  let dummy = new ListNode(-9999);
  dummy.next = head;
  
  let pre = dummy;
  let cur = head;
  
  while(cur!=null && cur.next!=null){
    if(cur.val == cur.next.val){
      let temp = cur.next;
      while(temp!=null && temp.val == cur.val)
        temp = temp.next;
      pre.next = temp;
      cur = temp;
    }else{
      pre = pre.next;
      cur = cur.next;
    }
  }
  return dummy.next;
}
module.exports = {
    deleteDuplicates : deleteDuplicates
};

另一种

function deleteDuplicates( head ) {
  if(head==null || head.next==null)  return head;
  
  let empty = new ListNode(-100),
      pre = empty;
  
  while(head){
    let flag = false;
    let val = head.val;
    let temp = head.next;
    
    while(temp && temp.val == val){
      flag = true;
      temp = temp.next;
    }
    if(flag==false){
      pre.next = head;
      head = head.next;
      pre = pre.next;
    }else{
      head = temp;
    }
  }
  pre.next = null;
  return empty.next;
}