Which structure estimates how many requests each of millions of IP addresses has made, in fixed memory?

Options

• ✓ A count-min sketch Correct
• ✗ A HyperLogLog
• ✗ A Bloom filter
• ✗ A trie

Why

A count-min sketch estimates per-item frequencies. HyperLogLog estimates how many distinct items there are, not how often each appears, and a Bloom filter only answers "seen or not".

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