Evaluate a Calculator / Expression

Question

## Problem

Implement a calculator evaluating an expression with +, -, *, / and parentheses.

## Example
```
"3+2*2" -> 7; "(1+(4+5+2)-3)+(6+8)" -> 23
```

## Constraints
- Valid expression, integer division truncates

## Approach
Two stacks (values/ops) or recursion; handle precedence and parentheses. Common Databricks problem.