Insight · ★★★★☆ · ~8 min
Intersecting Pillars
N pillars, sightlines block each other — how many mutually-visible pairs at most?
by MindYourPuzzle
N vertical pillars of various heights are arranged in a row. Two pillars "see" each other if no pillar between them is taller than both. How many pairs of pillars can see each other?
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