PHP 堆栈实现

Question

我想构建一个用 PHP 实现的堆栈。最初我有这个代码：

class Stack
{
    protected $stack;
    protected $limit;

    public function __construct($limit = 10) {
        // initialize the stack
        $this->stack = array();
        // stack can only contain this many items
        $this->limit = $limit;
    }

    public function push($item) {
        // trap for stack overflow
        if (count($this->stack) < $this->limit) {
            // prepend item to the start of the array
            array_unshift($this->stack, $item);
        } else {
            throw new RunTimeException('Stack is full!');
        }
    }

    public function pop() {
        if ($this->isEmpty()) {
            // trap for stack underflow
          throw new RunTimeException('Stack is empty!');
      } else {
            // pop item from the start of the array
            return array_shift($this->stack);
        }
    }

    public function top() {
        return current($this->stack);
    }

    public function isEmpty() {
        return empty($this->stack);
    }
}

然后用这个正常初始化类：

$stack = new Stack();
$stack->push(1);
$stack->push(2);
$stack->push(3);
$stack->push(4);
$stack->push(5);

这是正确的并且正在运行。但是，我想用这样的初始值初始化我的堆栈：

$stack = new Stack(array(1,2,3,4,5));

我该如何实现？

---

请注意，所有其他功能（例如 pop 和 push）都是正常的。

Answer 1

如下改变你的构造函数：

<?php

class Stack {

    protected $stack;
    protected $limit;

    public function __construct($limit = 10, $initial = array()) {
        // initialize the stack
        $this->stack = $initial;
        // stack can only contain this many items
        $this->limit = $limit;
    }

    public function push($item) {
        // trap for stack overflow
        if (count($this->stack) < $this->limit) {
            // prepend item to the start of the array
            array_unshift($this->stack, $item);
        } else {
            throw new RunTimeException('Stack is full!');
        }
    }

    public function pop() {
        if ($this->isEmpty()) {
            // trap for stack underflow
            throw new RunTimeException('Stack is empty!');
        } else {
            // pop item from the start of the array
            return array_shift($this->stack);
        }
    }

    public function top() {
        return current($this->stack);
    }

    public function isEmpty() {
        return empty($this->stack);
    }

}

/**
 * This'll work as expected.
 */
$stack = new Stack();
$stack->push(1);
$stack->push(2);
$stack->push(3);
$stack->push(4);
$stack->push(5);

/**
 * And this too.
 */
$stack = new Stack(10, array(1, 2, 3, 4, 5));

仅供参考，PHP 有 array_push (http://php.net/manual/en/function.array-push.php) 和 array_pop (http://us3.php.net/array_pop) 实现。

Answer 2

这是正确堆栈类的实现。要将数组正确初始化为堆栈的值，您必须像这样反转该数组的值：

class Stack
{
    protected $stack;
    protected $limit;

    public function __construct($values = array(),$limit = 10) {
        // initialize the stack
        $this->stack = array_reverse($values);
        // stack can only contain this many items
        $this->limit = $limit;
    }

    public function push($item) {
        // trap for stack overflow
        if (count($this->stack) < $this->limit) {
            // prepend item to the start of the array
            array_unshift($this->stack, $item);
        } else {
            throw new RunTimeException('Stack is full!');
        }
    }

    public function pop() {
        if ($this->isEmpty()) {
            // trap for stack underflow
          throw new RunTimeException('Stack is empty!');
      } else {
            // pop item from the start of the array
            return array_shift($this->stack);
        }
    }

    public function top() {
        return current($this->stack);
    }

    public function isEmpty() {
        return empty($this->stack);
    }
}

编码愉快！

Answer 3

使用 php 的堆栈（过程方法）

$data_array = [];
$top = -1;

function push($top, $item, $data_array){
    global $top,$data_array;
    $top++;
    $data_array[$top] = $item;
    return $data_array;
}


function pop(){
    global $top,$data_array;
    if($top < 0)
        return -1;
    $top_item = $data_array[$top];
    unset($data_array[$top]);
    $top--;
    return $top_item;
}
push($top, 1, $data_array);
push($top, 2, $data_array);
push($top, 3, $data_array)

pop();

Answer 4

简单，改变你的构造函数：

public function __construct($limit = 10, $values = array()) {
    // initialize the stack
    $this->stack = $values;
    // stack can only contain this many items
    $this->limit = $limit;
}

Answer 5

将构造函数更改为此。有了这个，您可以在数组中不提供任何值、单个值或多个值。如果值计数大于限制，它将引发错误。

    public function __construct($limit = 10, $values = null) {
        // stack can only contain this many items
        $this->limit = $limit;
        // initialize the stack
        $this->stack = array();
        if (is_null($values)) $values = array();
        else if (!is_array($values)) $values = array($values);
        foreach ($values as $value) $this->push($value);
    }

好了，希望对你有帮助。