How to initialize N dimensional arrays in C without using loop

Question

I want to initalize a 3 x 3 matrix with first two rows as 0\'s and last row as 1\'s. I have declared a 2D array int matrix[3][3]

I want to initialize it wit

Answer 1

For an constant integer expression N (say a macro or an enum constant) you'd have to "unroll" the initializer. There are macro tricks to do this when N expands to a decimal constant, but they are a bit involved. P99 provides such macros, with that you could write

#define N 23

int matrix[N][N] = {
    [N-1] = P99_DUPL(N, 1),
};

This lets you easily change N if you need it without having to touch anything else in your code for the update.