package leetcode

import (
	"github.com/halfrost/LeetCode-Go/structures"
)

// ListNode define
type ListNode = structures.ListNode

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

func middleNode(head *ListNode) *ListNode {
	if head == nil || head.Next == nil {
		return head
	}
	p1 := head
	p2 := head
	for p2.Next != nil && p2.Next.Next != nil {
		p1 = p1.Next
		p2 = p2.Next.Next
	}
	length := 0
	cur := head
	for cur != nil {
		length++
		cur = cur.Next
	}
	if length%2 == 0 {
		return p1.Next
	}
	return p1
}