19 remove nth node from end of list

19. 删除链表的倒数第 N 个结点

go：

/**

 * Definition for singly-linked list.

 * type ListNode struct {

 *     Val int

 *     Next *ListNode

 * }
 */
func removeNthFromEnd(head *ListNode, n int) *ListNode {
    dummy := &ListNode{Next: head}
    fast := dummy
    slow := dummy

    for i := 0; i < n + 1; i++ {
        fast = fast.Next
    }

    for fast != nil {
        fast = fast.Next
        slow = slow.Next
    }

    slow.Next = slow.Next.Next
    
    return dummy.Next
}