remove-nth-node-from-end-of-list.go

package problem0019

/*
 * Definition for singly-linked list.
 * type ListNode struct {
 *     Val int
 *     Next *ListNode
 * }
 */

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

func removeNthFromEnd(head *ListNode, n int) *ListNode {
	d, headIsNthFromEnd := getDaddy(head, n)

	if headIsNthFromEnd {
		// 删除head节点
		return head.Next
	}

	d.Next = d.Next.Next

	return head
}

// 获取倒数第N个节点的父节点
func getDaddy(head *ListNode, n int) (daddy *ListNode, headIsNthFromEnd bool) {
	daddy = head

	for head != nil {
		if n < 0 {
			daddy = daddy.Next
		}

		n--
		head = head.Next
	}

	// n==0，说明链的长度等于n
	headIsNthFromEnd = n == 0

	return
}