Solution (leetcode-in-java 1.21 API)

java.lang.Object
- g0201_0300.s0224_basic_calculator.Solution

```
public class Solution
extends Object
```
224 - Basic Calculator.
Hard

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

Note: You are not allowed to use any built-in function which evaluates strings as mathematical expressions, such as eval().

Example 1:

Input: s = “1 + 1”

Output: 2

Example 2:

Input: s = " 2-1 + 2 "

Output: 3

Example 3:

Input: s = “(1+(4+5+2)-3)+(6+8)”

Output: 23

Constraints:
- 1 <= s.length <= 3 * 10⁵
- s consists of digits, '+', '-', '(', ')', and ' '.
- s represents a valid expression.
- '+' is not used as a unary operation (i.e., "+1" and "+(2 + 3)" is invalid).
- '-' could be used as a unary operation (i.e., "-1" and "-(2 + 3)" is valid).
- There will be no two consecutive operators in the input.
- Every number and running calculation will fit in a signed 32-bit integer.

- Constructor Summary
  
  Constructors
  Constructor Description
  
  Solution()
- Method Summary
  
  All Methods Instance Methods Concrete Methods
  Modifier and Type Method Description
  
  int calculate(String s)
  - Methods inherited from class java.lang.Object
    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail
- Solution
```
public Solution()
```

Method Detail
- calculate
```
public int calculate(String s)
```