package main

func conquerAndSort(head *ListNode, end *ListNode) *ListNode {
	if head == nil || head == end || head.Next == nil {
		return head
	}
	if head.Next == end {
		if end != nil {
			if head.Val > end.Val {
				head.Val, end.Val = end.Val, head.Val
			}
		}
		return head
	}
	if head.Next.Next == end {
		if head.Val > head.Next.Val {
			head.Next.Val, head.Val = head.Val, head.Next.Val
		}
		return head
	}
	slow, fast := head, head
	for fast.Next != nil && fast.Next.Next != nil {
		slow = slow.Next
		fast = fast.Next.Next
	}
	lastSlow := slow
	slow = slow.Next
	lastSlow.Next = nil
	a := conquerAndSort(head, nil)
	b := conquerAndSort(slow, end)
	if a.Val > b.Val {
		a, b = b, a
	}
	// a Val < b Val
	head = a
	cur := a
	a = a.Next
	for a != nil && b != nil {
		if a.Val > b.Val {
			cur.Next = b
			b = b.Next
		} else {
			cur.Next = a
			a = a.Next
		}
		cur = cur.Next
	}
	if a == nil {
		cur.Next = b
	} else {
		cur.Next = a
	}
	return head
}
func sortList(head *ListNode) *ListNode {
	return conquerAndSort(head, nil)
}

func main() {
	arr := []int{-1, 5, 3, 4, 0}
	checkLink(sortList(makeLink(arr)))
}