Schedule plane takeoffs and landings across N runways

Problem

Given N runways and M plane operations, schedule takeoffs and landings. A landing plane occupies a runway until it is moved to a dock; a departing plane frees its runway once airborne.

Constraints

• N runways, M operations
• A runway holds at most one plane at a time

Approach

• Track each runway's busy/free state over time
• Assign each incoming operation to a free runway; queue or delay when none is free
• Focus on the core scheduling logic rather than full class-level design