# Finding out all the expressions within brackets

Finding out all the expressions within brackets : I was actually asked to find out the smallest bracket expression within an expression, I have omitted the function to check for the smallest string and omitting spaces within the expression.

This was actually an interview question at a startup in Seawoods, Navi Mumbai.

Given an expression like `((a + b * d) * (x / 2)) * (1 + (y + (x - 2) / 10))`

the smallest expression within brackets is `x / 2`

and `x - 2`

.
If we can find all the expressions within the brackets, then finding the smallest ones is as simple enough by finding the length after removing the spaces.

```
<?php
$s = "((a + b * d) * (x / 2)) * (1 + (y + (x - 2) / 10))";
$b = [];
$j = 0;
$stack = [];
for ($i = 0; $i < strlen($s); $i++)
{
if ($s[$i] == '(')
{
$b[++$j] = '';
}
elseif ($s[$i] == ')')
{
$stack[] = ($b[$j--] .= ')');
}
for ($k = 1; $k <= $j; $k++)
{
$b[$k] .= $s[$i];
}
}
echo $s.PHP_EOL;
print_r($stack);
echo PHP_EOL;
?>
```

```
php brackets.php
((a + b * d) * (x / 2)) * (1 + (y + (x - 2) / 10))
Array
(
[0] => (a + b * d)
[1] => (x / 2)
[2] => ((a + b * d) * (x / 2))
[3] => (x - 2)
[4] => (y + (x - 2) / 10)
[5] => (1 + (y + (x - 2) / 10))
)
```