pq

type Elem interface {
	// SetIndex stores the int index.
	SetIndex(int)
	// Index returns the last given by SetIndex(int).
	Index() int
}

type ElemComparator func(a, b Elem) bool

type PQ interface {
	// Push adds the ele
	Push(Elem)
	// Pop returns the highest priority Elem in PQ.
	Pop() Elem
	// Len returns the number of elements in the PQ.
	Len() int
	// Update `fixes` the PQ.
	Update(index int)
}