Kth Largest Number in a Stream (medium)

Problem Statement #

Design a class to efficiently find the Kth largest element in a stream of numbers.

The class should have the following two things:

1. The constructor of the class should accept an integer array containing initial numbers from the stream and an integer ‘K’.
2. The class should expose a function add(int num) which will store the given number and return the Kth largest number.

Example 1:

Input: [3, 1, 5, 12, 2, 11], K = 4
1. Calling add(6) should return '5'.
2. Calling add(13) should return '6'.
2. Calling add(4) should still return '6'.
 

Try it yourself #

Try solving this question here:

Solution #

This problem follows the Top ‘K’ Elements pattern and shares similarities with Kth Smallest number.

We can follow the same approach as discussed in the ‘Kth Smallest number’ problem. However, we will use a Min Heap (instead of a Max Heap) as we need to find the Kth largest number.

Code #

Here is what our algorithm will look like:

Time complexity #

The time complexity of the add() function will be $O(logK)$ since we are inserting the new number in the heap.

Space complexity #

The space complexity will be $O(K)$ for storing numbers in the heap.