Multiple elevator coordination in LLD - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to assign an elevator to a request based on the nearest elevator.

LLD

def assign_elevator(request_floor, elevators):
    nearest = None
    min_distance = float('inf')
    for elevator in elevators:
        distance = abs(elevator.current_floor - [1])
        if distance < min_distance:
            min_distance = distance
            nearest = elevator
    return nearest

Drag options to blanks, or click blank then click option'

Aelevators

Belevator.current_floor

Cmin_distance

Drequest_floor

Attempts:

3 left

💡 Hint

Common Mistakes

Using elevator.current_floor instead of request_floor causes zero distance always.

Using min_distance or elevators in distance calculation is incorrect.

The request_floor is used to calculate the distance from each elevator's current floor to the requested floor.

2fill in blank

medium

Complete the code to update the elevator's direction after assigning a new target floor.

LLD

def update_direction(elevator, target_floor):
    if target_floor > elevator.current_floor:
        elevator.direction = [1]
    elif target_floor < elevator.current_floor:
        elevator.direction = 'down'
    else:
        elevator.direction = 'idle'

Drag options to blanks, or click blank then click option'

A'idle'

B'up'

C'down'

D'stop'

Attempts:

3 left

💡 Hint

Common Mistakes

Setting direction to 'idle' or 'down' incorrectly when target floor is higher.

Using undefined direction values.

If the target floor is above the current floor, the elevator should move 'up'.

3fill in blank

hard

Fix the error in the code that checks if an elevator can pick up a request on its way.

LLD

def can_pickup(elevator, request_floor):
    if elevator.direction == 'up' and elevator.current_floor <= [1] <= elevator.target_floor:
        return True
    elif elevator.direction == 'down' and elevator.target_floor <= [1] <= elevator.current_floor:
        return True
    return False

Drag options to blanks, or click blank then click option'

Arequest_floor

Belevator.current_floor

Celevator.target_floor

Delevator.direction

Attempts:

3 left

💡 Hint

Common Mistakes

Using elevator.current_floor or target_floor instead of request_floor in the condition.

Comparing direction as a floor number.

The request_floor should be checked if it lies between the current floor and target floor in the elevator's direction.

4fill in blank

hard

Fill both blanks to correctly update the elevator's target floors queue and direction after servicing a floor.

LLD

def service_floor(elevator, floor):
    if floor in elevator.target_floors:
        elevator.target_floors.remove([1])
    if not elevator.target_floors:
        elevator.direction = [2]

Drag options to blanks, or click blank then click option'

Afloor

B'idle'

C'stop'

Delevator.current_floor

Attempts:

3 left

💡 Hint

Common Mistakes

Removing elevator.current_floor instead of the serviced floor.

Setting direction to 'stop' which is not a valid state.

Remove the serviced floor from target_floors and set direction to 'idle' if no targets remain.

5fill in blank

hard

Fill all three blanks to implement a function that selects the best elevator for a request considering direction and distance.

LLD

def select_best_elevator(request_floor, elevators):
    best_elevator = None
    best_score = float('inf')
    for elevator in elevators:
        if elevator.direction == [1] and can_pickup(elevator, request_floor):
            score = abs(elevator.current_floor - [2])
        else:
            score = abs(elevator.current_floor - [3]) + 10
        if score < best_score:
            best_score = score
            best_elevator = elevator
    return best_elevator

Drag options to blanks, or click blank then click option'

A'up'

Brequest_floor

Celevator.target_floor

D'down'

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong direction string or floor variables in conditions.

Not adding penalty for elevators that cannot pick up.

The elevator moving 'up' and able to pick up the request is preferred. The score uses request_floor if pickup is possible, else target_floor plus penalty.