题解 | #删除链表的倒数第n个节点#

package main
import . "nc_tools"
/*
 * type ListNode struct{
 *   Val int
 *   Next *ListNode
 * }
 */

/**
  * 
  * @param head ListNode类 
  * @param n int整型 
  * @return ListNode类
*/
func removeNthFromEnd(head *ListNode, n int) *ListNode {
	if n <= 0 {
		return head
	}
	var p *ListNode
	var q *ListNode
	var preP *ListNode
	for ; n > 0; n-- {
		if q == nil {
			q = head
		} else {
			q = q.Next
		}
	}
	for q != nil {
		preP = p
		if p == nil {
			p = head
		} else {
			p = p.Next
		}
		q = q.Next
	}
	if preP == nil {
		tmp := head.Next
		head.Next = nil
		return tmp
	} else {
		if p != nil {
			preP.Next = p.Next
			p.Next = nil
		} else {
			preP.Next = nil
		}
		return head
	}
	// write code here
}