PHP中的資料結構：DS擴充

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　　PHP7以上才能安裝和使用該資料結構擴充，安裝比較簡單：

1. 運行命令 pecl install ds2. 在php.ini中添加 extension=ds.so3. 重啟PHP或重載配置

•  Collection Interface：包含本庫中所有資料結構通用功能的基本interface。 It guarantees that all structures are traversable, countable, and can be converted to json using json_encode().

  Ds\Collection implements Traversable , Countable , JsonSerializable {/* 方法 */abstract public void clear ( void )abstract public Ds\Collection copy ( void )abstract public bool isEmpty ( void )abstract public array toArray ( void )}

   

• Hashable Interface：which allows objects to be used as keys.

  Ds\Hashable {/* 方法 */abstract public bool equals ( object $obj )abstract public mixed hash ( void )}

   

• Sequence Interface：A Sequence 相當於一個一維的數字key數組, with the exception of a few characteristics:
  • Values will always be indexed as [0, 1, 2, …, size - 1].
  • Only allowed to access values by index in the range [0, size - 1].

  Use cases:

  • Wherever you would use an array as a list (not concerned with keys).
  • A more efficient alternative to SplDoublyLinkedList and SplFixedArray.

   

• Vector Class：Vector是自動成長和收縮的連續緩衝區中的一系列值。它是最有效順序結構，值的索引直接映射到緩衝區中索引，增長因子不綁定到特定的倍數或指數。其具有以下優缺點：

  • 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.
  • Capacity does not have to be a power of 2.
  • get(), set(), push(), pop() are all O(1).
  • 但是 shift(), unshift(), insert() and remove() are all O(n).
   

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

   　

• Deque Class：“雙端隊列”的縮寫，也用於Ds\Queue中，擁有head、tail兩個指標。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. 其具有以下優缺點：
• 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).
• 但Capacity must be a power of 2.insert() and remove() are O(n).
• Map Class：索引值對的連續集合，幾乎與數組相同。鍵可以是任何類型，但必須是唯一的。如果使用相同的鍵添加到map中，則將替換值。其擁有以下優缺點：
• Keys and values can be any type, including objects.
• Supports array syntax (square brackets).
• Insertion order is preserved.
• Performance and memory efficiency is very similar to an array.
• Automatically frees allocated memory when its size drops low enough.
• Can’t be converted to an array when objects are used as keys.
• Pair Class：A pair is used by Ds\Map to pair keys with values.

  Ds\Pair implements JsonSerializable {/* 方法 */public __construct ([ mixed $key [, mixed $value ]] )}

   

• Set Class：唯一值序列。 This implementation uses the same hash table as Ds\Map, where values are used as keys and the mapped value is ignored.其擁有以下優缺點：
• Values can be any type, including objects.
• Supports array syntax (square brackets).
• Insertion order is preserved.
• Automatically frees allocated memory when its size drops low enough.
• add(), remove() and contains() are all O(1).
• 但Doesn’t support push(), pop(), insert(), shift(), or unshift(). get() is O(n) if there are deleted values in the buffer before the accessed index, O(1) otherwise. 
• Stack Class： “last in, first out”集合，只允許在結構頂部進行訪問和迭代。

  Ds\Stack implements Ds\Collection {/* 方法 */public void allocate ( int $capacity )public int capacity ( void )public void clear ( void )public Ds\Stack copy ( void )public bool isEmpty ( void )public mixed peek ( void )public mixed pop ( void )public void push ([ mixed $...values ] )public array toArray ( void )}

   

• Queue Class：“first in, first out”集合，只允許在結構前端進行訪問和迭代。

  Ds\Queue implements Ds\Collection {/* Constants */const int MIN_CAPACITY = 8 ;/* 方法 */public void allocate ( int $capacity )public int capacity ( void )public void clear ( void )public Ds\Queue copy ( void )public bool isEmpty ( void )public mixed peek ( void )public mixed pop ( void )public void push ([ mixed $...values ] )public array toArray ( void )}

   

• PriorityQueue Class：優先順序隊列與隊列是非常相似的，但值以指定的優先順序被推入隊列，優先順序最高的值總是位於隊列的前面，同優先順序元素“先入先出”順序任然保留。在一個PriorityQueue上遞代是具有破壞性的，相當於連續彈出操作直到隊列為空白。Implemented using a max heap.

  Ds\PriorityQueue implements Ds\Collection {/* Constants */const int MIN_CAPACITY = 8 ;/* 方法 */public void allocate ( int $capacity )public int capacity ( void )public void clear ( void )public Ds\PriorityQueue copy ( void )public bool isEmpty ( void )public mixed peek ( void )public mixed pop ( void )public void push ( mixed $value , int $priority )public array toArray ( void )}

   

PHP中的資料結構：DS擴充