problem224

README

< Previous 　　　　　　　　　　　　　　　　 Next >

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.

Related Topics

[Stack] [Recursion] [Math] [String]

Similar Questions

1. Evaluate Reverse Polish Notation (Medium)
2. Basic Calculator II (Medium)
3. Different Ways to Add Parentheses (Medium)
4. Expression Add Operators (Hard)
5. Basic Calculator III (Hard)