4 coding questions in the assessment. The first two were LeetCode easy, then the third was a LeetCode medium.

Then, the last one was the hardest question I had ever received on a coding assessment. I could only find a link to the problem afterwards in an obscure programming forum.

Hard one - Beautiful Matrices:

Given an m x m matrix, imagine that there are submatrices within the matrix that are n x n, where m % n = 0. (You are given n).

The average value of the submatrix (n x n) is known as its "Beauty number". Sort the matrix from left to right (and back to the beginning and down, repeat) by sorting the submatrices on their beauty numbers.