transform matrix 2D to 1D

Question

I have an issue passing a matrix 2D to a vector(1D array)with function in C. There is the code of what i want to create:

#include 
#define N          


        

Answer 1

Iterate over the diagonals of the square, alternating direction each time.

Here's a complete, working example (in c99).

#include 

#define max(a, b) ((a) > (b) ? (a) : (b))
#define min(a, b) ((a) > (b) ? (b) : (a))

void dezigzag(int out[64], int in[8][8]) {
    int n = 0;
    for (int diag = 0; diag < 15; diag++) {
        for (int i = max(0, diag - 7); i <= min(7, diag); i++) {
            out[n++] = diag % 2 ? in[diag - i][i] : in[i][diag - i];
        }
    }
}

int main(int argc, char *argv[]) {
    int out[64] = {-1};
    int in[8][8];
    for (int i = 0; i < 64; i++) {
        in[i % 8][i / 8] = i;
    }
    dezigzag(out, in);
    for (int i = 0; i < 64; i++) {
        printf("%d: %d\n", i, out[i]);
    }
    return 0;
}