LeetCode 703: Kth Largest Element In A Stream — Step-by-Step Visual Trace

Easy — Heap | Priority Queue | Data Stream | Design

The Problem

Design a class that efficiently finds the kth largest element in a stream of integers, where new values are continuously added and we need to return the kth largest element after each addition.

Approach

Use a min-heap of size k to maintain the k largest elements seen so far. The root of this min-heap will always be the kth largest element, allowing constant-time retrieval after each insertion.

Time: O(log k) per add operation, O(n log k) for initialization · Space: O(k)

Code

import heapq



class KthLargest:

    def __init__(self, k: int, nums: List[int]):

        self.min_heap = []

        self.k = k



        for num in nums:

            self.add(num)



    def add(self, val: int) -> int:

        heapq.heappush(self.min_heap, val)



        if len(self.min_heap) > self.k:

            heapq.heappop(self.min_heap)



        return self.min_heap[0]



# Your KthLargest object will be instantiated and called as such:

# obj = KthLargest(k, nums)

# param_1 = obj.add(val)

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