Pick the fewest watch times so every alert window is being watched.

Each window needs at least one watch time inside it. One well-placed time can cover several overlapping windows — find the smallest set.

Practice — no rating pressure. Get as close to the optimum as you can; each play teaches the pattern.

Windows watched

0/7

Alert windows

[7,8]

[7,10]

[1,7]

[18,22]

[2,8]

[3,5]

[17,18]

Candidate watch times

The Watch — practice the decision, scored against the optimum

What does the The Watch puzzle teach?

Cover every alert window with the fewest watch times — sort windows by end, plant a point at the end of the first uncovered window. Stabbing by earliest start uses more points.

Why do interviews ask about this?

Interval point-cover (minimum arrows to burst balloons): the exchange-argument greedy — sort by end and stab at the end of the first uncovered interval — is provably optimal, while the tempting earliest-start greedy is not.

How is it scored?

The engine computes the provably-optimal answer for the exact instance you played (dynamic programming, shortest-path, or exhaustive search — never a heuristic) and scores your attempt as a percentage of it. No login needed to see your score.

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Practice0:00

The Watch · D1

Pick the fewest watch times so every alert window is being watched.

Each window needs at least one watch time inside it. One well-placed time can cover several overlapping windows — find the smallest set.

Practice — no rating pressure. Get as close to the optimum as you can; each play teaches the pattern.

Windows watched

0/7

Alert windows

[7,8]

[7,10]

[1,7]

[18,22]

[2,8]

[3,5]

[17,18]

Candidate watch times