NAME

heap - Binary heap (priority queue) with O(log n) operations

SYNOPSIS

use heap;

# Create a min-heap (smallest element at top)
my $min_heap = heap::new('min');

# Create a max-heap (largest element at top)
my $max_heap = heap::new('max');

# Push values - O(log n)
$min_heap->push(5);
$min_heap->push(3);
$min_heap->push(7);
$min_heap->push(1);

# Pop returns smallest (for min-heap) - O(log n)
print $min_heap->pop;   # 1
print $min_heap->pop;   # 3
print $min_heap->pop;   # 5
print $min_heap->pop;   # 7

# Peek without removing - O(1)
$min_heap->push(10);
print $min_heap->peek;  # 10

# Bulk operations
$min_heap->push_all(4, 2, 8, 6);

# Utility methods - O(1)
my $size = $min_heap->size;
my $empty = $min_heap->is_empty;
my $type = $min_heap->type;  # 'min' or 'max'
$min_heap->clear;

# Custom comparator for complex objects
my $heap = heap::new('min', sub {
    my ($a, $b) = @_;
    return $a->{priority} <=> $b->{priority};
});

$heap->push({ name => 'low',    priority => 10 });
$heap->push({ name => 'high',   priority => 1  });
$heap->push({ name => 'medium', priority => 5  });

print $heap->pop->{name};  # 'high'

DESCRIPTION

heap provides a binary heap implementation in C. A heap is a tree-based data structure that satisfies the heap property: in a min-heap, the parent is always smaller than its children; in a max-heap, the parent is always larger.

This makes heaps ideal for priority queues where you need efficient access to the minimum or maximum element.

Performance

• push: O(log n)

• pop: O(log n)

• peek: O(1)

• size/is_empty: O(1)

METHODS

heap::new($type, [$comparator])

Create a new heap.

my $min_heap = heap::new('min');              # Min-heap
my $max_heap = heap::new('max');              # Max-heap
my $custom   = heap::new('min', sub { ... }); # With comparator

Parameters:

• $type - Either 'min' or 'max'. Determines whether the smallest or largest element is at the top.

• $comparator - Optional. A code reference that takes two values and returns -1, 0, or 1 (like <=>). When provided, this is used instead of numeric comparison.

$heap->push($value)

Add an element to the heap. Returns the heap for method chaining.

$heap->push(42);
$heap->push($obj)->push($another);  # Chaining

$heap->push_all(@values)

Add multiple elements to the heap. Returns the heap for method chaining.

$heap->push_all(1, 2, 3, 4, 5);

$heap->pop

Remove and return the top element (minimum for min-heap, maximum for max-heap). Returns undef if the heap is empty.

my $min = $min_heap->pop;

$heap->peek

Return the top element without removing it. Returns undef if empty.

my $min = $min_heap->peek;

$heap->size

Returns the number of elements in the heap.

$heap->is_empty

Returns true if the heap has no elements.

$heap->clear

Remove all elements from the heap.

$heap->type

Returns the heap type as a string: 'min' or 'max'.

CUSTOM COMPARATORS

For objects or complex sorting, provide a comparator function:

# Sort by 'score' field, highest first (max-heap behavior)
my $leaderboard = heap::new('max', sub {
    my ($a, $b) = @_;
    return $a->{score} <=> $b->{score};
});

# Sort by string field
my $alpha_heap = heap::new('min', sub {
    my ($a, $b) = @_;
    return $a->{name} cmp $b->{name};
});

The comparator should return:

• -1 if $a should come before $b

• 0 if they are equal

• 1 if $b should come before $a

EXAMPLES

Simple Priority Queue

use heap;

my $pq = heap::new('min');
$pq->push(5);
$pq->push(1);
$pq->push(3);

while (!$pq->is_empty) {
    print $pq->pop, "\n";  # Prints: 1, 3, 5
}

Task Scheduler

use heap;

my $tasks = heap::new('min', sub {
    $_[0]->{due} <=> $_[1]->{due}
});

$tasks->push({ name => 'Report',  due => 1706745600 });
$tasks->push({ name => 'Meeting', due => 1706659200 });
$tasks->push({ name => 'Review',  due => 1706832000 });

# Process tasks in order of due date
while (!$tasks->is_empty) {
    my $task = $tasks->pop;
    print "Do: $task->{name}\n";
}

Finding K Largest Elements

use heap;

my @numbers = (3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5);
my $k = 3;

# Use min-heap of size k
my $heap = heap::new('min');
for my $n (@numbers) {
    $heap->push($n);
    if ($heap->size > $k) {
        $heap->pop;  # Remove smallest
    }
}

# Heap now contains k largest
my @largest;
while (!$heap->is_empty) {
    push @largest, $heap->pop;
}
print "@largest\n";  # 5 6 9

AUTHOR

LNATION E<email@lnation.org>

LICENSE

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

cpanm Ancient

perl -MCPAN -e shell
install Ancient