Leetcode Question 224 'Basic Calculator' in Python

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