int *matvec4(int *A, int *x, int n){
    int i,j;
    int *y = Malloc(n * sizeof(int));

    for(i=0; i<n ;i++)
        y[i] = 0;

    for(i=0; i<n; i++)
        for(j=0; j<n; j++){
            y[i] += A[i*n + j] * x[j];
        }
    return y;
}

int main(){
    int A[3][3] = {{1,2,3}, {4,5,6}, {7,8,9}};
    int x[3] = {2,3,4};
    int i, n  = 3;

    int *y = NULL;
    //y = matvec3(A, x, n);
    y = matvec4(&A[0][0], x, 3);
    printf("Ax = [");
    for(i=0; i<n ;i++)
        printf("%d," , y[i]);
    printf("]\n");


    free(y);
    return 0;
}