I have a Priority Queue in Scala that I define below. My goal is that when I call dequeue I get the triple that has the most minimum third element in that triple. I figured that using Ordering is the way to go, but I cannot seem to get it to work.
def orderByWeight(lst : (Int, Int, Int)) = lst._3
val pq = new PriorityQueue[(Int, Int, Int)]()(Ordering.by(orderByWeight))
var x = ListBuffer((0,1,2), (0,2,3), (0,3,4))
x.map(i => pq.enqueue(i))
(0, 1, 2)
If you want all the 3-tuples dequeued in order of smalled 3rd element to largest, I think this is all you need.
val pq = PriorityQueue[(Int, Int, Int)]()(Ordering.by(-_._3))
If you need an ordered output in case of 3rd-element ties, you can expand it.
var x = ListBuffer((0,1,2), (0,2,3), (0,3,4), (1,0,2)) val pq = PriorityQueue(x:_*)(Ordering[(Int, Int)].on(x => (-x._3, -x._2)))