用PHP实现的四则运算表达式计算实现代码
author:一佰互联 2019-04-30   click:156
PHP实现:
复制代码 代码如下:
<?php
/**
* 计算四则运算表达式
*/
error_reporting(E_ALL);
$exp = "(1+2*(3+5)/4)*(3+(5-4)*2)";
$arr_exp = array();
for($i=0;$i<strlen($exp);$i++){
$arr_exp[] = $exp[$i];
}
$result = calcexp( array_reverse($arr_exp) );
echo $exp . "=" . $result;
function calcexp( $exp ){
$arr_n = array();
$arr_op = array();
while( ($s = array_pop( $exp )) != "" ){
if( $s == "(" ){
$temp = array(); $quote = 1; $endquote = 0;
while( ($t = array_pop($exp)) != "" ){
if( $t == "(" ){
$quote++;
}
if( $t == ")" ){
$endquote++;
if( $quote == $endquote ){
break;
}
}
array_push($temp, $t);
}
$temp = array_reverse($temp);
array_push($arr_n, calcexp($temp) );
}else if( $s == "*" || $s == "/" ){
$n2 = array_pop($exp);
if( $n2 == "(" ){
$temp = array(); $quote = 1; $endquote = 0;
while( ($t = array_pop($exp)) != "" ){
if( $t == "(" ){
$quote++;
}
if( $t == ")" ){
$endquote++;
if( $quote == $endquote )
break;
}
array_push($temp, $t);
}
$temp = array_reverse($temp);
$n2 = calcexp($temp);
}
$op = $s;
$n1 = array_pop($arr_n);
$result = operation($n1, $op, $n2);
array_push($arr_n, $result);
}elseif( $s == "+" || $s == "-" ){
array_push($arr_op, $s);
}else{
array_push($arr_n, $s);
}
}
$n2 = array_pop($arr_n);
while( ($op = array_pop($arr_op)) != "" ){
$n1 = array_pop($arr_n);
$n2 = operation($n1, $op, $n2);
}
return $n2;
}
function operation( $n1, $op, $n2 ){
switch ($op) {
case "+":
return intval($n1) + intval($n2);
break;
case "-":
return intval($n1) - intval($n2);
break;
case "*":
return intval($n1) * intval($n2);
break;
case "/":
return intval($n1) / intval($n2);
break;
}
}

这个实现方式中使用了两个堆栈,一个用来存储数字,一个用来存储运算符,遇到括号以后就递归进入括号内运算,实现方式有点笨拙,后面补充一下“逆波兰表达式”的算法实现。