The SplMinHeap class

    (PHP 5 >= 5.3.0, PHP 7, PHP 8)

    Introduction

    The SplMinHeap class provides the main functionalities of a heap, keeping the minimum on the top.

    Class synopsis

    class SplMinHeap extends SplHeap {
    /* Methods */
    protected compare(mixed $value1, mixed $value2): int
    /* Inherited methods */
    protected SplHeap::compare(mixed $value1, mixed $value2): int
    public SplHeap::count(): int
    public SplHeap::current(): mixed
    public SplHeap::extract(): mixed
    public SplHeap::insert(mixed $value): true
    public SplHeap::isCorrupted(): bool
    public SplHeap::isEmpty(): bool
    public SplHeap::key(): int
    public SplHeap::next(): void
    public SplHeap::recoverFromCorruption(): true
    public SplHeap::rewind(): void
    public SplHeap::top(): mixed
    public SplHeap::valid(): bool
    }

    Table of Contents

    • SplMinHeap::compare — Compare elements in order to place them correctly in the heap while sifting up

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    User Contributed Notes 2 notes

    up
    3
    gom
    5 years ago
    I experimented what happens when arrays are inserted:

    <?php
    $heap     = new SplMinHeap();
    $heap->insert([22,333]);
    $heap->insert([2,33]);
    $heap->insert([222,3]);

    var_export($heap->extract());
    echo     '<br>';
    var_export($heap->extract());
    echo     '<br>';
    var_export($heap->extract());
    ?>

    Output:

    array ( 0 => 2, 1 => 33, )
    array ( 0 => 22, 1 => 333, )
    array ( 0 => 222, 1 => 3, )
    up
    0
    andy at nospam dot airslash dot net
    1 hour ago
    To expand on gom's comment, SplMinHeap will also take into account the subsequent elements of the array you inserted, if the elements before that are equal.

    <?php
    $heap     = new SplMinHeap();
    $heap->insert([0, 10]);
    $heap->insert([0, 30]);
    $heap->insert([0, 15]);
    while (!    $heap->isEmpty()) {
    [    $a, $b] = $heap->extract();
    echo     "a:$a, b:$b\n";
    }
    echo     "---\n";
    $heap->insert([0, 10, 100]);
    $heap->insert([0, 10, 300]);
    $heap->insert([0, 10, 150]);
    while (!    $heap->isEmpty()) {
    [    $a, $b, $c] = $heap->extract();
    echo     "a:$a, b:$b, c:$c\n";
    }
    ?>

    will output:

    a:0, b:10
    a:0, b:15
    a:0, b:30
    ---
    a:0, b:10, c:100
    a:0, b:10, c:150
    a:0, b:10, c:300
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