← 返回 netflix 的题目列表Basic Calculator
类型：qbank
Evaluate a string expression with +, -, parentheses and unary minus without eval(); a stack handles nested parentheses and sign state.
Examples
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 * 10^5
s consists of digits, '+', '-', '(', ')', and ' '.
s represents a valid expression.
'+' is not used as a unary operation (i.e., "+1" and "+(2 + 3)" are invalid).
'-' could be used as a unary operation (i.e., "-1" and "-(2 + 3)" are valid).
There will be no two consecutive operators in the input.
Every number and running calculation will fit in a signed 32-bit integer.