package main
import . "nc_tools"
func deleteNode( head *ListNode ,  val int ) *ListNode {
    //1.开头
    //2.中间、末尾
    cur := &ListNode{Val:-1}
    cur.Next = head
    sentry := cur
    prev := cur
    for cur != nil {
        if cur.Val == val {
            prev.Next = cur.Next
        }
        prev = cur
        cur = cur.Next
    }
    return sentry.Next
}