标签：ace pop express put output exp bsp == integer
Implement a basic calculator to evaluate a simple expression string.
The expression string may contain open ( and closing parentheses ), the plus + or minus sign -, non-negative integers and empty spaces .
Example 1:
Input: "1 + 1" Output: 2
Example 2:
Input: " 2-1 + 2 " Output: 3
Example 3:
Input: "(1+(4+5+2)-3)+(6+8)" Output: 23
Note:
eval built-in library function.class Solution(object): def calculate(self, s): """ :type s: str :rtype: int """ sign = 1 res = 0 stack = [] index = 0 while index < len(s): char = s[index] if char.isdigit(): num = int(char) while index + 1 < len(s) and s[index + 1].isdigit(): num = 10 * num + int(s[index + 1]) index += 1 res += sign * num elif char == ‘+‘: sign = 1 elif char == ‘-‘: sign = -1 elif char == ‘(‘: stack.append(res) stack.append(sign) res = 0 sign = 1 elif char == ‘)‘: res = stack.pop() * res + stack.pop() index += 1 return res
标签：ace pop express put output exp bsp == integer
原文地址：https://www.cnblogs.com/xuanlu/p/11828694.html
