leetcode_gym/_problems/kthlargestElementInAnArray.md

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layout	title	last_solved	category	leetcode_url	status
page	Kth Largest Element in an Array		heap	https://leetcode.com/problems/kth-largest-element-in-an-array/	Attempted

Problem

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.

Example 1:

Input: [3,2,1,5,6,4] and k = 2
Output: 5
Example 2:

Input: [3,2,3,1,2,4,5,5,6] and k = 4
Output: 4

Solution

• If you're trying to find the largest kth element, use a min heap.
• As you're adding elements, evict elements if length is greater than k
• The result is the kth largest element sitting at the root

{% highlight python %}

def findKthLargest(self, nums: List[int], k: int) -> int:

min_heap = []

for n in nums:
    
    heapq.heappush(min_heap, n)
    
    print(min_heap) # added element n
    
    # if len>5, pop the smallest element (make room for a LARGER one)
    if len(min_heap)>k:
        heapq.heappop(min_heap)
    
    print(min_heap)
    print()
    
return heapq.heappop(min_heap)  # can also do `return min_heap[0]`

{% endhighlight %}

Your input
[3,2,1,5,6,4]
k=2

stdout
[3]
[3]

[2, 3]
[2, 3]

[1, 3, 2]
[2, 3]

[2, 3, 5]
[3, 5]

[3, 5, 6]
[5, 6]

[4, 6, 5]
[5, 6]