Lane Control OOD: Multi-Lane Traffic Management System

Question

## Problem

Design a `LaneController` for a highway with `n` lanes. Vehicles enter and exit lanes. Each lane has a capacity. Support queries for the lane with the most available space, merging two adjacent lanes, and reporting congestion alerts when any lane exceeds 80% capacity.

```python
class LaneController:
    def __init__(self, n: int, capacity_per_lane: int): ...

def vehicle_enter(self, lane: int) -> bool:
        """Add vehicle to lane. Return False if at capacity."""
        ...

def vehicle_exit(self, lane: int) -> bool:
        """Remove vehicle from lane. Return False if lane is empty."""
        ...

def most_available_lane(self) -> int:
        """Return lane index with the most free space."""
        ...

def merge_lanes(self, lane_a: int, lane_b: int) -> None:
        """Merge two adjacent lanes into one with combined capacity."""
        ...

def get_congestion_alerts(self) -> list[int]:
        """Return list of lane indices exceeding 80% capacity."""
        ...
```

```
lc = LaneController(3, 10)
lc.vehicle_enter(0)  # 7 times
lc.get_congestion_alerts()  -> [0]  # 7/10 = 70%? No, 8/10=80% triggers.
```

## Follow-ups

1. How does a priority queue help with `most_available_lane` if lanes update frequently?
2. How do you handle `merge_lanes` when vehicles must be redistributed?
3. How would you make this thread-safe for concurrent highway simulations?
4. Extend to support per-vehicle-type restrictions (e.g., lane 0 for trucks only).

Lane Control OOD: Multi-Lane Traffic Management System

Question Details

Full Details

About This Question

Topics

More Zoox Interview Questions