Leetcode 1106. Parsing A Boolean Expression

Posted 2021-08-11 SnailTyan

文章作者：Tyan
博客：noahsnail.com  |  CSDN  |  简书

1. Description

2. Solution

**解析：**Version 1，使用栈来求解，当碰到逻辑运算、(以及操作数时，入栈，当每次碰到)时，先将操作数出栈，然后再将逻辑运算出栈，计算逻辑运算的结果，将结果压入栈中，最终，栈中只剩下最终结果。

• Version 1

class Solution:
    def parseBoolExpr(self, expression: str) -> bool:
        operations = []
        for i in range(len(expression)):
            if expression[i] == '&' or expression[i] == '|' or expression[i] == '!' or expression[i] == '(':
                operations.append(expression[i])
            elif expression[i] == 't':
                operations.append(True)
            elif expression[i] == 'f':
                operations.append(False)
            elif expression[i] == ')':
                operators = []
                while operations[-1] != '(':
                    operators.append(operations.pop(-1))
                operations.pop(-1)
                logic = operations.pop(-1)
                if logic == '&':
                    temp = True
                    for val in operators:
                        temp &= val
                elif logic == '|':
                    temp = False 
                    for val in operators:
                        temp |= val
                else:
                    temp = not operators[-1]
                operations.append(temp)

        return operations[-1]

Reference

1. https://leetcode.com/problems/parsing-a-boolean-expression/