堆疊 (Stack)
實作 LIFO (last-in first-out) 順序，
如同一疊鬆餅，最後疊上去的鬆餅會最先被吃掉。
It uses the following operations:
- pop(): Remove the top item from the stack.
- push(item): Add an item to the top of the stack.
- peek(): Return the top of the stack.
- isEmpty(): Return true if and only if the stack is empty.
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| <?php
class Stack
{
protected ?StackNode $top;
public function pop()
{
if (is_null($this->top)) {
throw new Exception('Empty Stack');
}
$item = $this->top->data;
$this->top = $this->top->next;
return $item;
}
public function push($item)
{
$stackNode = new StackNode($item);
$stackNode->next = $this->top;
$this->top = $stackNode;
}
public function peek()
{
if (is_null($this->top)) {
throw new Exception('Empty Stack');
}
return $this->top->data;
}
public function isEmpty()
{
return is_null($this->top);
}
}
class StackNode
{
public mixed $data;
public ?StackNode $next;
public function __construct($data)
{
$this->data = $data;
$this->next = null;
}
}
|
佇列 (Queue)
實作 FIFO (first-in first-out) 順序，
如同售票亭前排隊，最先排隊的人最早拿到票。
It uses the following operations:
- add(item): Add an item to the end of the queue.
- remove(): Remove the first item of the queue.
- peek(): Return the first of the queue.
- isEmpty(): Return true if and only if the queue is empty.
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| <?php
class Queue
{
protected ?QueueNode $first;
protected ?QueueNode $last;
public function add($item)
{
$queueNode = new QueueNode($item);
if (!is_null($this->last)) {
$this->last->next = $queueNode;
}
$this->last = $queueNode;
if (is_null($this->first)) {
$this->first = $queueNode;
}
}
public function remove()
{
if (is_null($this->first)) {
throw new Exception('No Such Element');
}
$item = $this->first->data;
$this->first = $this->first->next;
if (is_null($this->first)) {
$this->last = null;
}
return $item;
}
public function peek()
{
if (is_null($this->first)) {
throw new Exception('No Such Element');
}
return $this->first->data;
}
public function isEmpty()
{
return is_null($this->first);
}
}
class QueueNode
{
public mixed $data;
public ?QueueNode $next;
public function __construct($data)
{
$this->data = $data;
$this->next = null;
}
}
|
ʕ •ᴥ•ʔ：程式碼可參考：CtCI-6th-php。