The Weekly Challenge 329

The Strategy: Both solutions follow the same logic: replace all non-digit characters (regex \D or [^0-9]) with spaces. Split the resulting string by whitespace to get individual number chunks. Maintain a "seen" set/hash to filter out duplicates while preserving the original order of first appearance.

sub counter_integers {
    my ($str) = @_;
    my $digits_as_spaces = $str =~ s/\D+/ /gr;
    my %seen;
    my @uniq;
    for my $chunk (split /\s+/, $digits_as_spaces) {
        next unless length $chunk;
        next if $seen{$chunk}++;
        push @uniq, 0 + $chunk;
    }
    return \@uniq;
}

def counter_integers(text: str) -> list[int]:
    digits_as_spaces = "".join(ch if ch.isdigit() else " " for ch in text)
    seen = set()
    result = []
    for chunk in digits_as_spaces.split():
        if chunk not in seen:
            seen.add(chunk)
            result.append(int(chunk))
    return result

The Strategy: A simple brute-force approach works well for strings of reasonable length. We iterate through all possible substrings (start and end indices). For each candidate, we check if it is "nice" by verifying that for every unique character in the substring, its lowercase and uppercase counterparts are also present. We keep track of the longest nice substring found.

sub is_nice {
    my ($s) = @_;
    my %letters;
    $letters{$_}++ for split //, $s;
    for my $ch (keys %letters) {
        return 0 unless exists $letters{lc $ch} && exists $letters{uc $ch};
    }
    return 1;
}

sub longest_nice_substring {
    my ($s) = @_;
    my $best = '';
    for my $start (0 .. length($s) - 1) {
        for my $end ($start + 1 .. length($s)) {
            my $candidate = substr $s, $start, $end - $start;
            next if length($candidate) <= length($best);
            $best = $candidate if is_nice($candidate);
        }
    }
    return $best;
}

def is_nice(s: str) -> bool:
    chars = set(s)
    return all(c.lower() in chars and c.upper() in chars for c in chars)

def longest_nice_substring(s: str) -> str:
    best = ""
    n = len(s)
    for i in range(n):
        for j in range(i + 1, n + 1):
            candidate = s[i:j]
            if len(candidate) > len(best) and is_nice(candidate):
                best = candidate
    return best