Basic Calculator

Easy

Given a string s representing a valid mathematical expression, implement a basic calculator to evaluate it and return the result.

The expression can contain:

Digits 0-9
+ and - operators
Parentheses ( and )
Spaces

The expression is guaranteed to be valid.

Example 1

Input

s = "1 + 1"

Output

Explanation

The expression contains two numbers joined by +, so the result is 1 + 1 = 2.

Example 2

Input

s = "(1+(4+5+2)-3)+(6+8)"

Output

Explanation

First evaluate the expressions inside the parentheses and then apply the surrounding + and - operations. The final result is 23.

Constraints

1 <= s.length <= 3 * 10^5

s consists of digits

'+'

'-'

'('

')'

and spaces.

s represents a valid expression.

'+' is not used as a unary operator.

'-' may be used as a unary operator.

There are no two consecutive operators in the expression.

Hints:

Hint 1

Scan the expression from left to right while maintaining the current number, sign, and accumulated result.

Hint 2

Use a stack to save the result and sign before entering a parenthesized expression, then combine them when the closing parenthesis is reached.

Author & Technical Reviewer

Technically reviewed by: ExamAdda Technical Review Team

Technical Reviewers, ExamAdda

Software engineers at ExamAdda who check every article's definitions, complexity claims and code examples before and after publishing.

Published

Aug 18, 2026

Last updated

Aug 18, 2026

Content Verification Methodology

Definitions and complexity claims were checked against authoritative computer-science references. Code examples were compiled and tested with standard, boundary and edge-case inputs.

Report a correction:editorial@examadda.org

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Input

Expected Output