#!/usr/bin/perl

$filename = "16.txt";

open(FILE, $filename);
@data = <FILE>;
close(FILE);

%rules = ();
$myticket = "";
@tickets = ();
@validtickets = ();
%ruleorder = ();
@ra = ();

# Read the file into variables.

foreach $line (@data) {
        $line =~ s/\n//sgi;
        $line =~ s/\r//sgi;
        $line =~ s/\t//sgi;

        # Rule description

        if ($line =~ m/^([a-z ]*): (\d+)-(\d+) or (\d+)-(\d+)$/) {
                $rules{$1} = $2."-".$3."-".$4."-".$5;
        }

        # A ticket line. If my ticket is not set, the line is first ticket line, thus its MY ticket.

        if ($line =~ m/^\d+,\d+,\d+,\d+,\d+,\d+,\d+,\d+,\d+,\d+,\d+,\d+,\d+,\d+,\d+,\d+,\d+,\d+,\d+,\d+$/) {
                if (length($myticket) < 20) {
                        $myticket = $line;
                }
                else
                {
                        push(@tickets, $line);
                }
        }
}

$scanerror = 0;

# Loop through all OTHER tickets.
foreach $ticket (@tickets) {
        @fields = split(",",$ticket);
        $vticket = 1;

        foreach $field (@fields) {

                # Loop through all fields in ticket.
                $valid = 0;
                foreach $rule (keys %rules) {
                        # Check field against all rules.
                        ($lowa, $higha, $lowb, $highb) = split("-", $rules{$rule});
                        if (((int($field) >= $lowa)&&(int($field) <= $higha)) || ((int($field) >= $lowb)&&(int($field) <= $highb))) {
                                $valid = 1;
                        }
                }
                if ($valid == 0) {
                        # If all rules are invalid, then the field is invalid, add it to scan error rate.
                        $scanerror = $scanerror + int($field);
                        $vticket = 0;
                }
        }
        if ($vticket == 1) {
                # Ticket is valid - theres no invalid fields in ticket. Add it to valid ticket tally for part 2.
                push(@validtickets, $ticket);
        }
}

print "P1: $scanerror \n";

$totalrulecount = 0;

# This is like soduku - multiple rules are valid for fields, but in such a way that if you "spend" the rules in the right order, there will only be one rule that is valid excluding the spent fields.

while ($totalrulecount < 20) { # If we found the order for all rules, we are done.

        @rulecount = ();
        for ($i = 0; $i < 20; $i++) { # Loop through all fields
                $foundrule = "";

                foreach $rulename (keys %rules) {
                        if ($ruleorder{$rulename} > 0) {
                                next; # Rule is spent - skip it.
                        }
                        $validrule = 0;
                        ($lowa, $higha, $lowb, $highb) = split("-", $rules{$rulename});

                        foreach $validticket (@validtickets) {
                                @fields = split(",",$validticket);
                                if (((int($fields[$i]) >= $lowa)&&(int($fields[$i]) <= $higha)) || ((int($fields[$i]) >= $lowb)&&(int($fields[$i]) <= $highb))) {
                                        $validrule++;
                                }
                        }

                        if ($validrule == ($#validtickets + 1)) { # If rule is valid for all tickets, we add it to rulecount.
                                $rulecount[$i]++;
                                $foundrule = $rulename;
                        }
                }

                if ($rulecount[$i] == 1) { # If there is only one rule that is valid for all tickets, not two or more, add it to ruleorder.
                        $ruleorder{$foundrule} = $i + 1;
                        $totalrulecount++;
                }
        }
}

# Add the fields to @ra - in the order as specified by the %ruleorder hash array.

for ($i = 1; $i < 21; $i++) {
        foreach $r (keys %ruleorder) {
                if ($ruleorder{$r} == $i) {
                        push(@ra, $r);
                }
        }
}

@myticketfields = split(",",$myticket);

$totalsum = 1;

# Multiple all departure fields

for ($i = 0; $i < 20; $i++) {
        if ($ra[$i] =~ m/^departure/) {
                $totalsum = $totalsum * int($myticketfields[$i]);
        }
}

print "P2: $totalsum \n";