19. 删除链表的倒数第N个节点

    /**
     * Definition for singly-linked list.
     * type ListNode struct {
     *     Val int
     *     Next *ListNode
     * }
     */
    func removeNthFromEnd(head *ListNode, n int) *ListNode {
        var nodes []*ListNode
        cur := head
        for cur != nil {
            nodes = append(nodes, cur)
            cur = cur.Next
        }
        removedHeadIndex := len(nodes) - n
        if removedHeadIndex == 0 {
            if removedHeadIndex + 1 < len(nodes) {
                return nodes[removedHeadIndex + 1]
            }
            return nil
        }
        if removedHeadIndex + 1 >= len(nodes) {
            nodes[removedHeadIndex - 1].Next = nil
        } else {
            nodes[removedHeadIndex - 1].Next = nodes[removedHeadIndex + 1]
        }
        
        return head
    }