The SplDoublyLinkedList class
(PHP 5 >= 5.3.0)
Introduction
The SplDoublyLinkedList class provides the main functionalities of a doubly linked list.
Class synopsis
/* Methods */
}Table of Contents
- SplDoublyLinkedList::add — Add/insert a new value at the specified index
- SplDoublyLinkedList::bottom — Peeks at the node from the beginning of the doubly linked list
- SplDoublyLinkedList::__construct — Constructs a new doubly linked list
- SplDoublyLinkedList::count — Counts the number of elements in the doubly linked list.
- SplDoublyLinkedList::current — Return current array entry
- SplDoublyLinkedList::getIteratorMode — Returns the mode of iteration
- SplDoublyLinkedList::isEmpty — Checks whether the doubly linked list is empty.
- SplDoublyLinkedList::key — Return current node index
- SplDoublyLinkedList::next — Move to next entry
- SplDoublyLinkedList::offsetExists — Returns whether the requested $index exists
- SplDoublyLinkedList::offsetGet — Returns the value at the specified $index
- SplDoublyLinkedList::offsetSet — Sets the value at the specified $index to $newval
- SplDoublyLinkedList::offsetUnset — Unsets the value at the specified $index
- SplDoublyLinkedList::pop — Pops a node from the end of the doubly linked list
- SplDoublyLinkedList::prev — Move to previous entry
- SplDoublyLinkedList::push — Pushes an element at the end of the doubly linked list
- SplDoublyLinkedList::rewind — Rewind iterator back to the start
- SplDoublyLinkedList::serialize — Serializes the storage
- SplDoublyLinkedList::setIteratorMode — Sets the mode of iteration
- SplDoublyLinkedList::shift — Shifts a node from the beginning of the doubly linked list
- SplDoublyLinkedList::top — Peeks at the node from the end of the doubly linked list
- SplDoublyLinkedList::unserialize — Unserializes the storage
- SplDoublyLinkedList::unshift — Prepends the doubly linked list with an element
- SplDoublyLinkedList::valid — Check whether the doubly linked list contains more nodes
Коментарии
FIFO and LIFO in SplDoublyLinkedList
$list = new SplDoublyLinkedList();
$list->push('a');
$list->push('b');
$list->push('c');
$list->push('d');
echo "FIFO (First In First Out) :\n";
$list->setIteratorMode(SplDoublyLinkedList::IT_MODE_FIFO);
for ($list->rewind(); $list->valid(); $list->next()) {
echo $list->current()."\n";
}
Result :
// FIFO (First In First Out):
// a
// b
// c
// d
echo "LIFO (Last In First Out) :\n";
$list->setIteratorMode(SplDoublyLinkedList::IT_MODE_LIFO);
for ($list->rewind(); $list->valid(); $list->next()) {
echo $list->current()."\n";
}
Result :
// LIFO (Last In First Out):
// d
// c
// b
// a
/*
php doubly link list is an amazing data structure ,doubly means you can traverse forward as well as backward, it can act as a deque(double ended queue) if you want it to,
here is how it works
*/
//instantiating an object of doubly link list
$dlist=new SplDoublyLinkedList();
//a push inserts data at the end of the list
$dlist->push('hiramariam');
$dlist->push('maaz');
$dlist->push('zafar');
/* the list contains
hiramariam
maaz
zafar
*/
//while an unshift inserts an object at top of the list
$dlist->unshift(1);
$dlist->unshift(2);
$dlist->unshift(3);
/* the list now contains
3
2
1
hiramariam
maaz
zafar
*/
//you can delete an item from the bottom of the list by using pop
$dlist->pop();
/* the list now contains
3
2
1
hiramariam
maaz
*/
//you can delete an item from the top of the list by using shift()
$dlist->shift();
/* the list now contains
2
1
hiramariam
maaz
*/
/* if you want to replace an item at particular index you can use a method named add , note that if you want to replace an item that does not exist , an exception will be thrown*/
$dlist->add(3 , 2.24);
/*
to go through the list we use a simple for loop, the rewind() method shown below point to the initials of the list depending on the iterator, a valid() method checks whether a list is still valid or not , meaning it ensures the loop does not go on and on after we reach the last data in the list , and the next() method simply points to the next data in the list.
*/
for($dlist->rewind();$dlist->valid();$dlist->next()){
echo $dlist->current()."<br/>";
}
echo "<br/>";
/*
To traverse backward
*/
$dlist->setIteratorMode(SplDoublyLinkedList::IT_MODE_LIFO);
for($dlist->rewind();$dlist->valid();$dlist->next()){
echo $dlist->current()."<br/>";;
}
<?php$splDoubleLinkedList = new SplDoublyLinkedList();
$splDoubleLinkedList->push('a');
$splDoubleLinkedList->push('3');
$splDoubleLinkedList->push('v');
$splDoubleLinkedList->push('1');
$splDoubleLinkedList->push('p');
//First of all, we need rewind list
$splDoubleLinkedList->rewind();
//Use while, check if the list has valid node
while ($splDoubleLinkedList->valid()){
//Print current node's value
echo $splDoubleLinkedList->current()."\n";
//Turn the cursor to next node
$splDoubleLinkedList->next();
}
?>
$a = new SplDoublyLinkedList;
$arr=[1,2,3,4,5,6,7,8,9];
for($i=0;$i<count($arr);$i++){
$a->add($i,$arr[$i]);
}
$a->push(11); //push method
$a->add(10,12); //add method must with index
$a->shift(); //remove array first value
$a->unshift(1); //add first value
$a->rewind(); //initial from first
echo "SplDoublyLinkedList array last/top value " . $a->top() ." \n";
echo "SplDoublyLinkedList array count value " . $a->count() ." \n";
echo "SplDoublyLinkedList array first/top value " . $a->bottom() . " \n\n";
while($a->valid()){ //check with valid method
echo 'key ', $a->key(), ' value ', $a->current(),"\n"; //key and current method use here
$a->next(); //next method use here
}
$a->pop(); //remove array last value
print_r($a);
$s=$a->serialize();
echo $s;
//Output
SplDoublyLinkedList array last/top value 12
SplDoublyLinkedList array count value 11
SplDoublyLinkedList array first/top value 1
key 0 value 1
key 1 value 2
key 2 value 3
key 3 value 4
key 4 value 5
key 5 value 6
key 6 value 7
key 7 value 8
key 8 value 9
key 9 value 11
key 10 value 12
SplDoublyLinkedList Object
(
[flags:SplDoublyLinkedList:private] => 0
[dllist:SplDoublyLinkedList:private] => Array
(
[0] => 1
[1] => 2
[2] => 3
[3] => 4
[4] => 5
[5] => 6
[6] => 7
[7] => 8
[8] => 9
[9] => 11
)
)
i:0;:i:1;:i:2;:i:3;:i:4;:i:5;:i:6;:i:7;:i:8;:i:9;:i:11;
$list = new SplDoublyLinkedList();
for ($i = 0; $i < 2000001; $i++) {
$list->push($i);
}
$s = microtime(true);
//$res = $list->offsetGet(2000000); // spend 7 ms
$res = $list->offsetGet(0); // spend 0.07 ms
var_dump($res);
$e = microtime(true);
echo ($e - $s) * 1000;
A function which replaces some portion od doubly linked list (DLL) with items from specified array.
<?php
/**
* Replace some portion (specified by index and length) of DLL with items
* from the specified replacement array.
*/
public function dll_splice(
\SplDoublyLinkedList $dll,
int $start,
int $length,
array $replacement,
): void {
if ($start < 0 || ($start + $length) > $dll->count()) {
throw new \OutOfRangeException("Invalid range for splicing");
}
for ($i = 0; $i < $length; $i++) {
$dll->offsetUnset($start);
}
foreach ($replacement as $item) {
$dll->add($start, $item);
}
}
?>