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namespace Ptypes; |
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use Ptypes\Exceptions\UnexpectedType; |
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use Ptypes\Exceptions\InvalidArgument; |
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use Ptypes\Exceptions\StackOverflow; |
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use Ptypes\Exceptions\StackUnderflow; |
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use Countable; |
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/** |
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* Stack is a last in first out (lifo) data type. |
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* |
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* functions: push, pop, is_empty, size, peek |
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*/ |
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class Stack implements Countable |
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{ |
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private $maxsize; |
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private $items; |
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private $top; |
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/** |
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* Stack is a last in first out (lifo) data type. |
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* |
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* @param int $maxsize |
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* |
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* @return Stack |
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*/ |
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public function __construct($maxsize) |
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{ |
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if(gettype($maxsize) != "integer"){throw new UnexpectedType("Expected an integer, got: ".gettype($maxsize));} |
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if($maxsize < 2) {throw new InvalidArgument("Stack has a minimum size of 2!");} |
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$this->maxsize = $maxsize; |
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$this->items = array(); |
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$this->top = 0; |
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} |
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/** |
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* Push (add) the item to the Stack. |
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* |
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* @param object $item |
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*/ |
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public function push($item) |
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{ |
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if($this->top == $this->maxsize) {throw new StackOverflow("Pushing this item would overflow the stack (exceed the max stack size)!");} |
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$this->items[$this->top++] = $item; |
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return $this; |
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} |
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/** |
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* Pop (remove) the top item from the Stack. |
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*/ |
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public function pop() |
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{ |
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if($this->top == 0) {throw new StackUnderflow("Cannot pop an empty stack!");} |
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unset($this->items[$this->top--]); |
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return $this; |
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} |
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/** |
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* is_empty tests whether the stack is empty. |
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* |
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* @return boolean |
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*/ |
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public function is_empty() |
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{ |
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return ($this->top == 0) ? true : false; |
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} |
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/** |
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* Size, returns the size of the stack. |
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* |
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* @return int |
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*/ |
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public function size() |
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{ |
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return $this->top; |
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} |
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/** |
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* Peek returns the top element of the stack, returns null if the stack is empty. |
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* |
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* @return object |
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*/ |
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public function peek() |
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{ |
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if($this->top == 0) {return null;} |
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return $this->items[$this->top-1]; |
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} |
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//Overriding functions & magic methods below |
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/** |
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* Count, same functionality as Size. |
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* Overrides the default count function call on this class. |
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* |
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* @return int |
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*/ |
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public function count() |
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{ |
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return $this->size(); |
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} |
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/** |
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* Overrides the default toString call on this class. |
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* |
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* @return string |
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*/ |
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public function __toString() |
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{ |
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$str = "Stack:\n"; |
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$str .= ((string)$this->items[$this->top-1])." <-- top\n"; |
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for($i = $this->top-2; $i >= 0; $i--) |
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{ |
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$str .= ((string)$this->items[$i])."\n"; |
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} |
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return $str; |
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} |
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} |
HOWZ1T /
Ptypes
