elevator_saga.js

about.md

Elevator Saga

A programming challenge for dispatching elevators. If you've ever waited for an elevator and thought about how much sorter the wait would be if you were the programmer, give this a try.

http://play.elevatorsaga.com/

About the Algorithm

This very simplistic implementation attempts to do just two things:

1. Always choose the elevator car with the fewest queued destinations.
2. Never push a destination onto the queue if it's already there.

When ran against their examples it's clear that the first elevator is constantly working hard while the remaining elevators sit mostly idle. A naive round-robin approach might work better than attempting to identify nearly-idle elevators.

About the Implementation

elevator_saga.js

{
    init: function(elevators, floors) {
        _.each(elevators,function(elevator) {
            elevator.on('floor_button_pressed',function(floorNum){
                if(!elevator.destinationQueue.includes(floorNum)) {
                    elevator.goToFloor(floorNum);
                }
            });
        });

        _.each(floors, function(floor) {
            floor.on('up_button_pressed down_button_pressed', function() {
                var assigned = _.sortBy(elevators, function(elevator) {
                    elevator.destinationQueue.length;
                })[0];
                var floorNum = floor.floorNum();
                if(!assigned.destinationQueue.includes(floorNum)) {
                   assigned.goToFloor(floorNum);
                }
            });
        });
    },
    update: function(dt, elevators, floors) {
        // We normally don't need to do anything here
    }
}