Spot-the-Pattern Drills

Intermediate · 30 min read · Interview Playbook, Interview Playbook

Sixty unseen problem statements: name the pattern in under a minute, then check.

Recognising the pattern is the skill interviews test first, and it's the one people practise least: they solve problems one topic at a time, so they always know which pattern is coming. These 60 statements are mixed, the way problems arrive in a real interview.

Many statements are paraphrased from Cracking the Coding Interview (6th ed.) and carry its problem number, so you can find the full problem and solution there. The rest are interview classics.

How to use these drills

The rounds get harder, and every round mixes topics on purpose.

Round 1: warm-up

Round 2: arrays and strings in disguise

Round 3: linked lists, stacks and searching

Round 4: graphs, trees and DP

Round 5: medium-hard mix

Round 6: hard and advanced

Further reading

Key takeaways

• Practise spotting separately from solving: name the pattern, the signal and the target complexity in under a minute.
• Score each drill 2, 1 or 0; every 1 is a look-alike you should study.
• Write the missed signal in your log; redo the set a week later in a new order.
• Mixed practice is what makes recognition work under interview pressure.

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