题解 | #调整牛群顺序#

package main

import (
	. "nc_tools"
)

/*
 * type ListNode struct{
 *   Val int
 *   Next *ListNode
 * }
 */

/**
 * 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
 */
func moveNthToEnd( head *ListNode ,  n int ) *ListNode {
    // write code here
    l, r := head, head
    for i := 0; i < n-1; i ++ {
        r = r.Next
    }
    var prev *ListNode
    for r.Next != nil {
        prev = l
        l = l.Next
        r = r.Next
    }
    if prev != nil {
        r.Next = l
        prev.Next = l.Next
        l.Next = nil
    } else {
        r.Next = l
        head = l.Next
        l.Next = nil
    }
    return head
}