function dist([r1, c1], [r2, c2], empty, expan) {
const dy = empty.rows.reduce(
(acc, val) =>
Math.min(r1, r2) < val && val < Math.max(r1, r2) ? acc + expan : acc,
0
);
const dx = empty.cols.reduce(
(acc, val) =>
Math.min(c1, c2) < val && val < Math.max(c1, c2) ? acc + expan : acc,
0
);
return Math.abs(r2 - r1) + dy + Math.abs(c2 - c1) + dx;
}