Calculation of four arithmetic expressions using PHP_PHP tutorial

Question requirements: There is a string expression of four arithmetic operations, write a function to calculate the result of the four arithmetic operations

PHP implementation:

1

2

3 /**

4 * Calculate four arithmetic expressions

5*/

6

7 error_reporting(E_ALL);

8

9 $exp = '(1+2*(3+5)/4)*(3+(5-4)*2)';

10 $arr_exp = array();

11

12 for($i=0;$i

13 $arr_exp[] = $exp[$i];

14}

15 $result = calcexp( array_reverse($arr_exp) );

16 echo $exp . '=' . $result;

17

18 function calcexp( $exp ){

19​​ $arr_n = array();

20 $arr_op = array();

21 

22 while( ($s = array_pop( $exp )) != '' ){

23 if( $s == '(' ){

24               $temp = array(); $quote = 1; $endquote = 0;

25               while( ($t = array_pop($exp)) != '' ){

26                if( $t == '('){

27                 $quote++;

28 }

30

32 break;

33              }

34 }

35     array_push($temp, $t);

36 }

37               $temp = array_reverse($temp);

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

39    }else if( $s == '*' || $s == '/' ){

40               $n2 = array_pop($exp);

41               if( $n2 == '('){

42                    $temp = array(); $quote = 1; $endquote = 0;

43                     while( ($t = array_pop($exp)) != '' ){

44 if( $t == '(' ){

45                     $quote++;

46 }

47                                                                                                                                                                                                                                          

51                     }

52                     array_push($temp, $t);

53                 }

54                 $temp = array_reverse($temp);

55                 $n2 = calcexp($temp);

56             }

57            

58             $op = $s;

59             $n1 = array_pop($arr_n);

60            

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

62             array_push($arr_n, $result);

63         }elseif( $s == '+' || $s == '-' ){

64             array_push($arr_op, $s);

65         }else{

66             array_push($arr_n, $s);

67         }

68     }

69    

70     $n2 = array_pop($arr_n);

71     while( ($op = array_pop($arr_op)) != '' ){

72         $n1 = array_pop($arr_n);

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

74     }

75    

76     return $n2;

77 }

78

79 function operation( $n1, $op, $n2 ){

80     switch ($op) {

81         case '+':

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

83             break;

84         case '-':

85             return intval($n1) - intval($n2);

86             break;

87         case '*':

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

89             break;

90         case '/':

91             return intval($n1) / intval($n2);

92             break;

93     }

94 }

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。