Find the $k^{th}$ smallest element in an $(n \times n)$ matrix, where each row and column of the matrix is sorted in ascending order.

Although there can be repeating values in the matrix, each element is considered unique and, therefore, contributes to calculating the $k^{th}$ smallest element.

Constraints:

• n $==$ matrix.length
• n $==$ matrix[i].length
• $1\leq$ n $\leq100$
• $-10^3\leq$ matrix[i][j] $\leq10^3$
• $1\leq$ k $\leq n^2$

A key observation when tackling this problem is that the matrix is sorted along rows and columns. This means that whether we look at the matrix as a collection of rows or as a collection of columns, we see a collection of sorted ...