AlgoSolveoRoadmap › Stage 7: Heaps & Backtracking › Pattern 31 of 53
DSA pattern guide
Heap — Top K Elements
k largest/smallest/most frequent, k closest, merge k sorted lists.
Use it when
k largest/smallest/most frequent, k closest, merge k sorted lists.
Key idea
Keep a heap of size k so each push costs O(log k). Use a min-heap for the largest k.
Practice problems, in order
- Kth Largest Element in a StreamEasy
- Last Stone WeightEasy
- Top K Frequent ElementsMedium
- K Frequent WordsMedium
- Kth Largest Element in an ArrayMedium
- Find K Pairs with Smallest SumsMedium
- Find Median from Data StreamHard
- Merge K Sorted ListsHard
- Smallest Range Covering K ListsHard
How to practise this pattern
- Read the problem and look for the signal above before writing any code.
- Say the brute force out loud, with its time complexity, then ask what work it repeats.
- Apply the key idea and write the optimised version yourself.
- If you're stuck for more than 10 minutes, take one small hint, not the full solution.
- Move to the next problem only when you can explain why this pattern fits.
Stuck on one of these?
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