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);
}
}
并使用以下命令正常初始化类:
$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。然而,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(例如弹出和推送)都是可用的。
按如下方式更改构造函数:
<?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。
以下是正确堆栈类的实现。要将数组正确初始化为堆栈的值,您必须反转该数组的值,如下所示:
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);
}
}
编码快乐!
使用php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, $data_array)
pop();
简单,更改您的构造函数:
public function __construct($limit = 10, $values = array()) {
// initialize the stack
$this->stack = $values;
// stack can only contain this many items
$this->limit = $limit;
}
将构造函数更改为this。这样,您就可以在一个数组中不提供任何值、单个值或多个值。如果值的计数大于限制,它将抛出一个错误。
public function __construct($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);
}
希望它能有所帮助。