Basic Calculator — Step-by-Step Visualization

Algorithm Pattern

Stack + Sign Tracking

Key Idea

When encountering '(', save current state. On ')', restore and apply saved sign.

Step-by-Step Approach

1. Track current number, running result, and sign
2. On '(': push (result, sign), reset to fresh context
3. On ')': finalize number, pop saved context, combine with saved sign
4. Apply sign before each number

Common Gotchas

• Multi-digit numbers must be accumulated before applying to result.
• At ')' you must finalize the current number before popping.
• The sign before a '(' applies to the entire sub-expression inside.