Design an elevator system for a building with N lifts. When someone presses the call button, which lift answers, and where in your code is that decided?

Short answer

Split the decision in two. In an elevator system, each lift is a state machine that owns its position, direction and stop list, and decides on its own which floor comes next. A separate dispatcher answers the hall call: when someone presses up or down on a landing, it asks a strategy to score every in-service lift and adds the stop to the cheapest one. Buttons pressed inside a car skip the dispatcher entirely, because that passenger has already chosen their lift.