LeetCode 595: Big Countries

Meta Data

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Difficulty: easy First Attempt: 2021-10-10

• Submissions: Accepted ×3

Approach

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A country is big if either condition holds, so join them with OR (SQL Template 1). The problem says at least, so use >=.

My Attempts

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All three passed: OR, OR in the other order, and a UNION of two queries. They used > although the problem says “at least”; the boundary should be >=, which the tests happened not to probe.

Solution

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SELECT name, population, area
FROM World
WHERE area >= 3000000 OR population >= 25000000;

Complexity

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One table scan, O(n).

Mistakes to Avoid

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• “At least” means >=.
• Two queries with UNION can be faster with indexes, but OR is usually fine.

Interview Explanation

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I filter with WHERE for an area of at least three million or a population of at least twenty-five million and return the name, population and area.