题解 | #表达式求值#

#
# 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
#
# 返回表达式的值
# @param s string字符串 待计算的表达式
# @return int整型
#
class Solution:
    def solve(self , s: str) -> int:
        # write code here
        if '(' not in s:
            start = s.find('*')
            if start == -1:
                s = s.replace('+-', '-')
                s = s.replace('--', '+')
                start = s.find('+')
                if start == -1:
                    start = s.rfind('-')
                    if start == -1 or start == 0:
                        if s == '':
                            return 0
                        else:
                            return int(s)
                    else:                    
                        return self.solve(s[:start]) - self.solve(s[start + 1:])
                else:
                    return self.solve(s[:start]) + self.solve(s[start + 1:])
            else:
                left, right = s[:start], s[start + 1:]
                num1 = ''
                while left != '' and left[-1].isdecimal():
                    num1 = left[-1] + num1
                    left = left[:-1]
                num2 = ''
                while (right != '' and right[0].isdecimal()) or num2 == '':
                    num2 = num2 + right[0]
                    right = right[1:]
                return self.solve(left + str(int(num1) * int(num2)) + right)
        else:
            start = s.find('(')
            parse = 0
            for end in range(len(s)):
                if s[end] == '(':
                    parse += 1
                elif s[end] == ')':
                    parse -= 1
                    if parse == 0:
                        break
            sub_str = s[start + 1: end]
            val = self.solve(sub_str)
            if val == 6:
                print(val)
            new_str = s[:start] + str(val) + s[end + 1:]
            return self.solve(new_str)