Description
Given a string s representing a valid expression, implement a basic calculator to evaluate it. The expression may contain '(', ')', '+', '-', and non-negative integers. Return the result as an integer.
Examples
Input:
s = "1 + 1"Output:
2Explanation:
1 + 1 = 2.
Input:
s = " 2-1 + 2 "Output:
3Explanation:
Evaluating left to right: 2 - 1 = 1, then 1 + 2 = 3. Whitespace is ignored during parsing.
Input:
s = "(1+(4+5+2)-3)+(6+8)"Output:
23Explanation:
Inner parentheses first: (4+5+2) = 11, then (1+11-3) = 9, and (6+8) = 14. Finally 9 + 14 = 23.
Constraints
- •
1 ≤ s.length ≤ 3 × 10⁵ - •
s consists of digits, '+', '-', '(', ')', and ' '.