Time Complexity: O(m * n), where m is the number of rows and n is the number of columns in the matrix. This is because we are iterating through each element of the matrix once.

Space Complexity: O(1), as we are not using any additional data structures that grow with the input size. We are only using a constant amount of space for the loop variables.

Optimal Approach

Algorithm

This method is simple and time efficient.
First, traverse the first row by fixing the row index as 0.
Next, traverse the last column by fixing the column index as n-1.
Then, traverse the last row by fixing the row index as m-1.
Finally, traverse the first column by fixing the column index as 0.
By following this approach, we can avoid traversing the whole matrix to find the boundary elements.

Code

1234567891011121314151617181920212223242526272829303132</