Print matrix diagonally practice

main.rs

pub fn print_matrix_diag(mm: &[&[usize]]) {
  assert!(mm.len() > 0);

  let xdim = mm[0].len();
  let ydim = mm.len();
  let maxdim = xdim + ydim - 1;

  println!("---");
  for i in 0..maxdim {
    print_el(mm, i as isize, 0, xdim, ydim);
    println!("");
  }
  println!("---");
}

fn print_el(mm: &[&[usize]], x: isize, y: isize, xdim: usize, ydim: usize) {
  if x < 0 { return }

  if x < xdim as isize && y < ydim as isize && y >= 0 {
    print!("{:?} ", mm[y as usize][x as usize]);
  }

  print_el(mm, x - 1, y + 1, xdim, ydim);
}

fn main() {
  let matrix: [&[usize]; 3] = [
    &[1, 2],
    &[3, 4],
    &[5, 6]
  ];

  let matrix0: [&[usize]; 3] = [
    &[1, 2, 3],
    &[4, 5, 6],
    &[7, 8, 9]
  ];

  let matrix1: [&[usize]; 5] = [
    &[1 ,2 ,3 ,4 ,5 ,6 ],
    &[7 ,8 ,9 ,10,11,12],
    &[13,14,15,16,17,18],
    &[19,20,21,22,23,24],
    &[25,26,27,28,29,30]
  ];

  let matrix2: [&[usize]; 7] = [
    &[1],
    &[2],
    &[3],
    &[4],
    &[5],
    &[6],
    &[7],
  ];

  println!("");
  print_matrix_diag(matrix.as_ref());
  print_matrix_diag(matrix0.as_ref());
  print_matrix_diag(matrix1.as_ref());
  print_matrix_diag(matrix2.as_ref());

  assert!(false);
}