链表的基本操作

单链表添加节点

function insert(head,val){
  const newNode = listNode(9)
  const cur = head
  while(head.next && !cur === val){
        cur = head.next
  }
  const next = cur.next
  newNode.next = next
  cur.next = newNode
  return head
}

在链表头部添加

const newNode = listNode(0)
newNode.next = head
head = newNode
return head

在链表尾部添加

while(head.next){
    // 移动 head 指针
    head = head.next;
}
// 新节点插入尾部
head.next = newNode;

单链表删除节点

function deleteNode(head, val){
  if(head === null) return
  let prev = null
  let cur = head
  while(head.next && cur !== val){
    prev = cur
    cur = head.next
  }
  prev.next = cur.next
  return head
}