137. Top K Frequent Elements

PRO

Medium

Topics

Companies

Helpful tools to learn & understand

Visualize LogicActive Simulator

Watch key transitions, pointers, and variables update step-by-step.

Open

Check Solutions

Read clean, documented implementations across multiple patterns.

View Code

Thinkpad (Draw & Note)

Sketch diagrams on an infinite canvas and draft notes directly inline.

Draw

Example 1:

Input: nums = [1,1,1,2,2,3], k = 2

Output: [1,2]

Explanation: The elements 1 and 2 appear most frequently. 1 appears 3 times, 2 appears 2 times, and 3 appears once. Since k=2, we return the two most frequent elements [1, 2].

Example 2:

Input: nums = [1], k = 1

Output: [1]

Explanation: The element 1 appears once. Since k=1, we return [1].

Example 3:

Input: nums = [4,1,-1,2,2,2,3], k = 2

Output: [2, 1]

Explanation: 2 appears 3 times, 1 appears 1 time, -1 appears 1 time, 4 appears 1 time, 3 appears 1 time. The two most frequent elements are 2 and 1.

Constraints:

•
•
•

Time Complexity

O(n log k)

Space Complexity

O(n + k)