用PHP实现的四则运算表达式计算实现代码

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];

}

$result = calcexp( array_rever($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;

}
已知关于x的方程
}

array_push($temp, $t);

}

$temp = array_rever($temp);

array_push($arr_n, calcexp($temp) );

}el if( $s == ‘*’ || $s == ‘/’ ){

$n2 = array_pop($exp);

if( $n2 == ‘(‘ ){

$temp = array(); $quote = 1; $en离歌饶雪漫dquote = 0;

while( ($t = array_pop($exp)) != ” ){

if( $t =大连燕窝岭= ‘(‘ ){

$quote++;

}

if( $t == ‘)’ ){

$endquote++;

if( $quote == $endquote )

break;

}

array_push($temp, $t);

}

$temp = array_rever($temp);

$n2 = calcexp($temp);

}

$op = $s;

$n1 = array_pop($arr_n);

$result = operation($n1, $op, $n2);

array_push($arr_n, $result);

}elif( $s == ‘+’ || $s == ‘-‘ ){

array_push($arr_op, $s);

}el{

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) {

ca R周末日记16;+’:

return intval($n1) + intval($n2);

break;

ca ‘-‘:

retu季风洋流rn intval($n1) – intval($n2);

break;

ca ‘*’:

return intval($n1) * intval($n2);

break;

ca ‘/’:

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。