The Deque class

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简介

A Deque (pronounced “deck”) is a sequence of values in a contiguous buffer that grows and shrinks automatically. The name is a common abbreviation of “double-ended queue” and is used internally by Ds\Queue.

Two pointers are used to keep track of a head and a tail. The pointers can “wrap around” the end of the buffer, which avoids the need to move other values around to make room. This makes shift and unshift very fast — something a Ds\Vector can’t compete with.

Accessing a value by index requires a translation between the index and its corresponding position in the buffer: ((head + position) % capacity).

Strengths

Supports array syntax (square brackets).
Uses less overall memory than an array for the same number of values.
Automatically frees allocated memory when its size drops low enough.
get(), set(), push(), pop(), shift(), and unshift() are all O(1).

Weaknesses

Capacity must be a power of 2.
insert() and remove() are O(n).

类摘要

Ds\Deque implements Ds\Sequence {

/* Constants */

const int MIN_CAPACITY = 8 ;

/* 方法 */

public void allocate ( int $capacity )

public void apply ( callable $callback )

public int capacity ( void )

public void clear ( void )

public bool contains ([ mixed $...values ] )

public Ds\Deque copy ( void )

public Ds\Deque filter ([ callable $callback ] )

public mixed find ( mixed $value )

public mixed first ( void )

public mixed get ( int $index )

public void insert ( int $index [, mixed $...values ] )

public bool isEmpty ( void )

public string join ([ string $glue ] )

public mixed last ( void )

public Ds\Deque map ( callable $callback )

public Ds\Deque merge ( mixed $values )

public mixed pop ( void )

public void push ([ mixed $...values ] )

public mixed reduce ( callable $callback [, mixed $initial ] )

public mixed remove ( int $index )

public void reverse ( void )

public Ds\Deque reversed ( void )

public void rotate ( int $rotations )

public void set ( int $index , mixed $value )

public mixed shift ( void )

public Ds\Deque slice ( int $index [, array $length ] )

public void sort ([ callable $comparator ] )

public Ds\Deque sorted ([ callable $comparator ] )

public number sum ( void )

public array toArray ( void )

public void unshift ([ mixed $values ] )

}

预定义常量

Ds\Deque::MIN_CAPACITY

Ds\Deque::allocate — Allocates enough memory for a required capacity.
Ds\Deque::apply — Updates all values by applying a callback function to each value.
Ds\Deque::capacity — Returns the current capacity.
Ds\Deque::clear — Removes all values from the deque.
Ds\Deque::__construct — Creates a new instance.
Ds\Deque::contains — Determines if the deque contains given values.
Ds\Deque::copy — Returns a shallow copy of the deque.
Ds\Deque::count — Returns the number of values in the collection.
Ds\Deque::filter — Creates a new deque using a callable to determine which values to include.
Ds\Deque::find — Attempts to find a value's index.
Ds\Deque::first — Returns the first value in the deque.
Ds\Deque::get — Returns the value at a given index.
Ds\Deque::insert — Inserts values at a given index.
Ds\Deque::isEmpty — Returns whether the deque is empty
Ds\Deque::join — Joins all values together as a string.
Ds\Deque::jsonSerialize — Returns a representation that can be converted to JSON.
Ds\Deque::last — Returns the last value.
Ds\Deque::map — Returns the result of applying a callback to each value.
Ds\Deque::merge — Returns the result of adding all given values to the deque.
Ds\Deque::pop — Removes and returns the last value.
Ds\Deque::push — Adds values to the end of the deque.
Ds\Deque::reduce — Reduces the deque to a single value using a callback function.
Ds\Deque::remove — Removes and returns a value by index.
Ds\Deque::reverse — Reverses the deque in-place.
Ds\Deque::reversed — Returns a reversed copy.
Ds\Deque::rotate — Rotates the deque by a given number of rotations.
Ds\Deque::set — Updates a value at a given index.
Ds\Deque::shift — Removes and returns the first value.
Ds\Deque::slice — Returns a sub-deque of a given range.
Ds\Deque::sort — Sorts the deque in-place.
Ds\Deque::sorted — Returns a sorted copy.
Ds\Deque::sum — Returns the sum of all values in the deque.
Ds\Deque::toArray — Converts the deque to an array.
Ds\Deque::unshift — Adds values to the front of the deque.

The Deque class

简介

Strengths

Weaknesses

类摘要

预定义常量

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