Top K Frequent Elements

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Solution Guide: Top K Frequent Elements

Approach

First count element frequencies using a hash map. Then use bucket sort where the bucket index represents frequency and the bucket contents are elements with that frequency. Collect elements from the highest-frequency buckets until k elements are gathered.

Complexity Analysis

Time
O(n)
Space
O(n)

Pattern

Frequency Count + Bucket Sort

Why It Works

Bucket sort avoids the O(n log n) cost of comparison-based sorting. Since frequencies are bounded by array length, creating buckets indexed by frequency enables linear-time extraction of the top k elements.

Updated Feb 2026