89. Top K Frequent Elements - Trending Items

You're building an analytics dashboard that shows trending products, most viewed pages, or popular content. You need to find the top K most frequently occurring items from a dataset.

Given an integer array nums and an integer k, return the k most frequent elements. You may return the answer in any order.

Requirements

1. Basic Functionality

• Count frequency of each element
• Find top K most frequent elements
• Return in any order
• Handle cases where k equals array length

Example Usage

topKFrequent([1,1,1,2,2,3], 2); // [1, 2] - 1 appears 3 times, 2 appears 2 times
topKFrequent([1], 1);           // [1]
topKFrequent([4,1,-1,2,-1,2,3], 2); // [-1, 2] - both appear twice

Real-World Context

This problem models real analytics features:

• Trending products: Show top K most viewed products
• Popular pages: Display most visited pages
• Content recommendations: Find most liked/shared content
• Analytics dashboard: Show top performing metrics