# Python heapq to find K’th smallest element in a 2D array

• Difficulty Level : Basic
• Last Updated : 28 Jul, 2022

Given an n x n matrix and integer k. Find the k’th smallest element in the given 2D array. Examples:

```Input : mat = [[10, 25, 20, 40],
[15, 45, 35, 30],
[24, 29, 37, 48],
[32, 33, 39, 50]]
k =  7
Output : 7th smallest element is 30```

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

We will use similar approach like K’th Smallest/Largest Element in Unsorted Array to solve this problem.

1. Create an empty min heap using heapq in python.
2. Now assign first row (list) in result variable and convert result list into min heap using heapify method.
3. Now traverse remaining row elements and push them into created min heap.
4. Now get k’th smallest element using nsmallest(k, iterable) method of heapq module.

Implementation:

## Python3

 `# Function to find K'th smallest element in``# a 2D array in Python``import` `heapq` `def` `kthSmallest(``input``):` `    ``# assign first row to result variable``    ``# and convert it into min heap``    ``result ``=` `input``[``0``]``    ``heapq.heapify(result)` `    ``# now traverse remaining rows and push``    ``# elements in min heap``    ``for` `row ``in` `input``[``1``:]:``        ``for` `ele ``in` `row:``            ``heapq.heappush(result,ele)` `    ``# get list of first k smallest element because``    ``# nsmallest(k,list) method returns first k``    ``# smallest element now print last element of``    ``# that list``    ``kSmallest ``=` `heapq.nsmallest(k,result)``    ``print` `(k,``"th smallest element is "``,kSmallest[``-``1``])` `# Driver program``if` `__name__ ``=``=` `"__main__"``:``    ``input` `=` `[[``10``, ``25``, ``20``, ``40``],``        ``[``15``, ``45``, ``35``, ``30``],``        ``[``24``, ``29``, ``37``, ``48``],``        ``[``32``, ``33``, ``39``, ``50``]]``    ``k ``=` `7``    ``kthSmallest(``input``)`

Output

`7 th smallest element is  30`

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