215 Kth Largest Element in an Array

Find the kth largest element in an unsorted array. Note that it is the kth largest element in the sorted order, not the kth distinct element.

For example, Given[3,2,1,5,6,4]and k = 2, return 5.

Note: You may assume k is always valid, 1 ≤ k ≤ array's length.

The Idea: Maintain the k largest elements using a min heap. If next element is larger top of the heap (minimum), then replace that element with the next largest element. In the end, the top of queue should have kth largest element where all the remaining elements in the queue are larger than it.

Complexity: O(nlog(k)) time and O(k) space

from queue import PriorityQueue


class Solution:
    def findKthLargest(self, nums, k):
        """
        :type nums: List[int]
        :type k: int
        :rtype: int
        """

        pq = PriorityQueue()
        for i, num in enumerate(nums):
            if pq.qsize() == k and pq.queue[0] < num:
                pq.get()
                pq.put(num)
            elif pq.qsize() < k:
                pq.put(num)
        return pq.queue[0]