function filterEquationBrackets($q)
{
$serializedEquation = serializeEquationToArray($q);
$equation = deserializeArrayToEquation($serializedEquation);
$filteredSerializedEquation = filterBracketBySerializedEquation($serializedEquation);
return deserializeArrayToEquation($filteredSerializedEquation);
}
function serializeEquationToArray($equation)
{
// rm unnecessary spaces and brackets
$equation = str_replace(' ', '', $equation);
$equation = str_replace('()', '', $equation);
// remove brackets if there is only one operator between brackets
$equation = preg_replace('/(\\()([\\+\\-\\*\\/]+)(\\))/', '$2', $equation);
// add '*' if no opeator between number and bracket
$equation = preg_replace('/(\\w|\\))(\\()/', '$1*(', $equation);
$equation = preg_replace('/(\\))(\\w)/', ')*$2', $equation);
// check total open and close bracket count, alert if not equal
$totalOpenBracketCount = preg_match_all('/\\(/', $equation, $a);
$totalCloseBracketCount = preg_match_all('/\\)/', $equation);
if ($totalOpenBracketCount != $totalCloseBracketCount) {
echo '<script>alert("invalid equation");</script>';
exit;
}
// init parameters
$rt = array();
$openBracketCount = 0;
$closeBracketCount = 0;
$openBracketPos = 0;
$closeBracketPos = 0;
// split $equation to characters
$characters = str_split($equation);
// process
foreach ($characters as $key => $c) {
// record the open bracket position
if ($c == '(') {
$openBracketCount++;
// only record the first open bracket position
if ($openBracketCount == 1) {
$openBracketPos = $key;
}
continue;
}
// if no bracket has been recorded, push the character into array
if ($openBracketCount == 0) {
$rt[] = $c;
continue;
}
// record the close bracket position
if ($c == ')') {
$closeBracketCount++;
$closeBracketPos = $key;
// if count of open and close bracket are equal, try to get sub equation
if ($openBracketCount == $closeBracketCount) {
// get sub equation
$startPos = $openBracketPos + 1;
$endPos = $closeBracketPos - 1;
$subEquation = '';
for ($i = $startPos; $i <= $endPos; $i++) {
$subEquation .= $characters[$i];
}
// serilize sub equation to array
$subRt = array('(');
$subRt = array_merge($subRt, serializeEquationToArray($subEquation));
$subRt[] = ')';
$rt[] = $subRt;
// reset open and close bracket count
$openBracketCount = 0;
$closeBracketCount = 0;
}
}
}
return $rt;
}
