Evaluate a Calculator / Expression

Problem
Implement a calculator that evaluates a string arithmetic expression with +, -, *, / and parentheses, respecting operator precedence.

Input / Output

• Input: a string expression (e.g. "3+2*2").
• Output: the evaluated integer result (integer division truncates toward zero).

Constraints

• The expression is valid; integer division truncates.
• Handle nested parentheses and precedence (*// bind tighter than +/-).

Example

• "3+2*2" → 7.
• "(1+(4+5+2)-3)+(6+8)" → 23.