Kth Largest Element In a Stream

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Problem

Design a class that finds the kth largest element in a growing stream of numbers. It should support adding a new number and, after each addition, returning the current kth largest value seen so far.

Examples

Example 1

Input:k = 3, nums = [4,5,8,2]; add(3)

Output:4

Example 2

Input:add(5); add(10)

Output:5, 5

Constraints

1 <= k <= 10^4
At most 10^4 calls to add.

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How to approach it: the Heap / Priority Queue pattern

A heap keeps the minimum (or maximum) element accessible in O(1), with O(log n) insert and remove. It's the tool whenever you repeatedly need "the smallest/largest remaining item" without needing everything fully sorted.

Look for this pattern when

You need the top-k largest/smallest elements, not a full sort.
You're merging multiple sorted sequences (always take the smallest available head).
You need a running min/max/median as data streams in.

Read the full Heap / Priority Queue guide →

Video walkthroughs

Original problem on LeetCode ↗