Which of the following sequences correctly orders the steps for the single-elevator algorithm to minimize wait times?

Which of the following sequences correctly orders the steps for the single-elevator algorithm to minimize wait times?

• A. I, II, III, IV
• B. I, IV, III, II
• C. II, I, III, IV
• D. IV, III, II, I

Answer: (B)

Minimizing wait times with a single-elevator strategy hinges on sweeping in one direction before turning around rather than hopping back and forth. The best sequence starts by establishing an initial target and direction, so the elevator commits to a path rather than oscillating. Next, it moves to the farthest floor required in that direction while picking up every pending call along the way. This step gathers as many riders as possible in one journey without stopping and reversing prematurely. After reaching that farthest point, the elevator reverses and finishes the remaining requests on the return path. This approach reduces unnecessary travel and direction changes, which cuts down on waiting for riders on both sides of the car’s path. Other sequences that reverse earlier or backtrack between floors create extra trips and longer waits for some calls.

Minimizing wait times with a single-elevator strategy hinges on sweeping in one direction before turning around rather than hopping back and forth. The best sequence starts by establishing an initial target and direction, so the elevator commits to a path rather than oscillating. Next, it moves to the farthest floor required in that direction while picking up every pending call along the way. This step gathers as many riders as possible in one journey without stopping and reversing prematurely. After reaching that farthest point, the elevator reverses and finishes the remaining requests on the return path. This approach reduces unnecessary travel and direction changes, which cuts down on waiting for riders on both sides of the car’s path. Other sequences that reverse earlier or backtrack between floors create extra trips and longer waits for some calls.