Return to Revisions

How can I decrease code length?

You could split your big for loop into 2 smaller ones. The first one would print all diagonals up to the main one, and the other one the remaining ones.

For instance, let's say there's a matrix like:

1 2 3
4 5 6
7 8 9

Then, your first loop would print 1 4 2 7 5 3 and the second one 8 6 9. The code would look conciser and more readable too:

for (int i = 0; i < N; i++) {
    for (int j = 0; j <= i; j++) {
        printf("%d ", pixel_array[i - j][j]);
    }
}

for (int j = 0; j < N - 1; j++) {
    for (int i = N - 1; i > j; i--) {
        printf("%d ", pixel_array[i][N - i + j]);
    }
}

How can I improve the efficiency of this program?

I don't think it's possible to make it more efficient than O(n²) as you have to go through all matrix elements to print them diagonally.

Any other programming practices to be implemented

Rather than using an int type for defining a size of your array, you could use uint32_t (or uint16_t or uint64_t - it depends on your requirements). You size cannot be negative, anyways.

As you currently define your logic in main() you could create a separate method instead like printDiagonally(int32_t** array, const uint32_t rows, const uint32_t columns). Then, you could use this method anywhere in your app.