AOC day 5 part 1 UNHOLY

666.rs

macro_rules! walker {
        // step
        ($steps:expr; $node:expr; [$($listB:tt),* $prev:expr]; [$next:expr, $($listF:expr),+]) => {
            match $steps {
                $steps if $steps == 0 => {
                    *$node + 1;
                    ($node - 1; $node; [$listB, $prev]; [$next, $listF];)
                },
                $steps if $steps > 0 => {
                    ($steps - 1; $next; [$listB, $prev, $node]; [$listF])
                },
                $steps if $steps < 0 => {
                    ($steps + 1; $prev; [$listB]; [$node, $next, $listF])
                },
            }
        };

        // 1st step case
        ($steps:expr; [$node:expr, $($listB:expr),*]; [$($listF:expr),+]) => {
            ($steps; $node; [$listB]; [$listF])
        };

        // after last step
        ($steps:expr; $node:expr; [$($listB:expr),*]; [$($listF:expr),*]) => {
            ($steps)
        };
    }