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【PHP】 PHP实现逆波兰式 - 计算工资时用

作者:邪恶的小Y / 发布于2011/10/9/ 652

<div><?php
/**
* math_rpn 
*
* 实现逆波兰式算法
* 
* @author sparkHuang <a href="mailto:2605588@qq.com">2605588@qq.com</a>
* @version RPN 1.0.0 
* 
*/</div>
<div>class math_rpn {
//初始的计算表达式
private $_expression = '';
//处理后的逆波兰表达式
private $_rpnexp = array();

//模拟栈结构的数组
private $_stack = array('#');

//正则判断
//private $_reg = '/^([A-Za-z0-9\(\)\+\-\*\/])*$/';

//优先级
private $_priority = array('#' => 0, '(' => 10, '+' => 20, '-' => 20, '*' => 30, '/' => 30);

//四则运算
private $_operator = array('(', '+', '-', '*', '/', ')');

public function __construct($expression) {
$this->_init($expression);
}

private function _init($expression) {
$this->_expression = $expression;
}

public function exp2rpn() {
$len = strlen($this->_expression);

for($i = 0; $i < $len; $i++) {
$char = substr($this->_expression, $i, 1);

if ($char == '(') {
$this->_stack[] = $char;
continue;
} else if ( ! in_array($char, $this->_operator)) {
$this->_rpnexp[] = $char;
continue;
} else if ($char == ')') {
for($j = count($this->_stack); $j >= 0; $j--) {
$tmp = array_pop($this->_stack);
if ($tmp == "(") {
break;
} else {
$this->_rpnexp[] = $tmp;
}
}
continue;
} else if ($this->_priority[$char] <= $this->_priority[end($this->_stack)]) {
$this->_rpnexp[] = array_pop($this->_stack);
$this->_stack[] = $char;
continue;
} else {
$this->_stack[] = $char;
continue;
}
}
for($i = count($this->_stack); $i >= 0; $i--) {
if (end($this->_stack) == '#') break;
$this->_rpnexp[] = array_pop($this->_stack);
}
return $this->_rpnexp;
}
}
<div>$expression = "(A*(B+C)-E+F)*G";
var_dump($expression);
$mathrpn = new math_rpn($expression);
var_dump($mathrpn->exp2rpn());</div>
<div>/*End of php*/</div>

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