题解 | 删除链表的倒数第n个节点

/**
 * class ListNode(var `val`: Int) {
 *     var next: ListNode? = null
 * }
 */
object Solution {
    /**
    * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
    *
    * 
        * @param head ListNode类 
        * @param n int整型 
        * @return ListNode类
    */
    fun removeNthFromEnd(head: ListNode?,n: Int): ListNode?  {
        // write code here
        if(head == null)return null
        var dummy = ListNode(0)
        dummy.next = head
        var fast:ListNode?=dummy
        var slow:ListNode?=dummy
        repeat(n+1){
            fast = fast?.next
        }
        while(fast!=null){
            fast = fast?.next
            slow = slow?.next
        }
        slow?.next = slow?.next?.next
        return dummy.next
        }
}