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  1. <?php
  2. //Code challenge
  3. //company: Sparkcentral
  4. //applicant:  Mike Roderick
  5.  
  6. class simpleCalculator{
  7.   private $str_calc;
  8.  
  9.   //constructor, accepts inoput string for calculation
  10.   public function simpleCalculator($str_input){
  11.     //remove whitespace and other undesireables, store result in private variable
  12.     $this->str_calc = preg_replace('/[^0-9%+-\/\*]/s', '', $str_input);
  13.     if (sizeof($this->str_calc) > 0){
  14.       print "successfully initialized.\nValue stored:".$this->str_calc."\n";
  15.       return true;
  16.     } else {
  17.       return false;
  18.     }
  19.   }
  20.  
  21.   public function calculateResult(){
  22.     //order of operations: multiplication, division and modulus, then addition and subtraction
  23.     $this->handleMath('*');
  24.     $this->handleMath('/');
  25.     $this->handleMath('%');
  26.     $this->handleMath('+');
  27.     $this->handleMath('-');
  28.     print "calculated value:".$this->str_calc."\n";
  29.   } 
  30.  
  31.   private function handleMath($operator){
  32.   	//Iterate over the equation, according to the operator that was passed in
  33.     while(strpos($this->str_calc,$operator) !== false){
  34.       //for debugging
  35.       //echo $this->str_calc."...";
  36.  
  37.       //find number1 and number2 based on operand
  38.       $operator_position = strpos($this->str_calc,$operator);
  39.  
  40.       //get the first number+position in this operation
  41.       $first_half = substr($this->str_calc,0,$operator_position);
  42.       $first_parts = preg_split("/[%+-\/\*]+/",$first_half);
  43.       $number1 = array_pop($first_parts);
  44.       $numberpos1 = strrpos($first_half,$number1);
  45.  
  46.       //get the second number+position in this operation
  47.       $second_half = substr($this->str_calc,$operator_position+1);
  48.       $second_parts = preg_split("/[%+-\/\*]+/",$second_half);
  49.       $number2 = array_shift($second_parts);
  50.       $numberpos2 = ($operator_position + 1) + strlen($number2);
  51.  
  52.       //do the math
  53.       $result = $this->mathOp($number1, $number2, $operator);
  54.  
  55.       //shoehorn the result back into the string
  56.       $this->str_calc = substr($this->str_calc,0,$numberpos1) . $result . substr($this->str_calc,$numberpos2);
  57.  
  58.       //for debugging
  59.       //print "becomes: ".$this->str_calc."\n";
  60.     }
  61.   }
  62.  
  63.   private function mathOp($number1, $number2, $operator){
  64.     switch($operator){
  65.       case '*':
  66.       	return $number1 * $number2;
  67.       	break;
  68.       case '/':
  69.       	return $number1 / $number2;
  70.       	break;
  71.       case '+':
  72.       	return $number1 + $number2;
  73.       	break;
  74.       case '-':
  75.       	return $number1 - $number2;
  76.       	break;
  77.       case '%':
  78.       	return $number1 % $number2;
  79.       	break;
  80.     }	
  81.   }
  82.  
  83. }
  84. echo 'starting...';
  85. $x = new simpleCalculator('a e q 5 + 9 - 4 * 2 / 4 % 5 * 2');
  86. $x->calculateResult();
  87. ?>
Success #stdin #stdout 0.02s 24400KB
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Standard input is empty
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starting...successfully initialized.
Value stored:5+9-4*2/4%5*2
calculated value:12
https://ideone.com/VHsAs5
language:
PHP (php 7.3.5)
created:
10 years ago
visibility:
public

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