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Kth Smallest Element in a Sorted Matrix

Question​

Given a n x n matrix where each of the rows and columns are sorted in ascending order, find the kth smallest element in the matrix.

Example 1
Input:

matrix = [
   [ 1,  5,  9],
   [10, 11, 13],
   [12, 13, 15]
],
k = 8

Output: 13

Solution​

all//Kth Smallest Element in a Sorted Matrix.py


def kthSmallest(matrix, k):

    # convert 2d matrix into 1d array
    arr = []
    for row in matrix:
        for ele in row:
            arr.append(ele)

    # sort the array
    arr.sort()

    # return kth smallest element
    return arr[k-1]

# Driver Code
matrix = [[2, 6, 8],
        [3, 7, 10],
        [5, 8, 11]]

k = 5
print(kthSmallest(matrix, k))

# Output: 7