func split(head *llNode) (left, right *llNode) {
	left = head
	if head == nil || head.next == nil {
		return
	}
	right = head
	sprinter := head
	prev := head
	for sprinter != nil && sprinter.next != nil {
		prev = right
		right = right.next
		sprinter = sprinter.next.next
	}
	prev.next = nil
	return
}
func split(head *llNode) (left, right *llNode) {
	left = head
	if head == nil || head.next == nil {
		return
	}
	right = head
	sprinter := head
	prev := head
	for sprinter != nil && sprinter.next != nil {
		prev = right
		right = right.next
		sprinter = sprinter.next.next
	}
	prev.next = nil
	return
}
func split ( head * llNode ) ( left , right * llNode ) { left = head if head == nil || head . next == nil { return } right = head sprinter := head prev := head for sprinter != nil && sprinter . next != nil { prev = right right = right . next sprinter = sprinter . next . next } prev . next = nil return }
// split breaks a list in half.
split breaks a list in half .