How to work on a sub-matrix in a matrix by pointer?

Question

I have a matrix of size n. Take an example:

My recursive function does the processing on the elements that lie in the border of the matrix. Now I want to c

Answer 1

I am not sure of your application, but I wonder if using #define for your matrix size would help....

#define X_SIZE 4
#define Y_SIZE 4

or even

#define N_SIZE 4

... because then you can use X_SIZE and Y_SIZE (OR N_SIZE) in your function without having to pass them explicitly.

in main you might put

 int matrix[X_SIZE * Y_SIZE];

or

int matrix2[N_SIZE * N_SIZE];

then you can call the ith row and jth column element with

*(pmatrix + X_SIZE*j + i) 

or

matrix[X_SIZE*j + i] 

or

*(pmatrix2 + N_SIZE*j + i)

or

matrix2[N_SIZE*j + i]

where pmatrix and pmatrix2 are pointers to matrix and matrix2.

I am pretty sure there is no clever trick to be able to easily pass the inner square 2x2 matrix to a function, unless you were to copy the elements from the centre of your matrix into a new matrix and then copy back the result afterwards.