代码随想录训练营第III期--011--python

 # 代码随想录训练营第III期--011--python

#  20. 有效的括号
class Solution:
    def isValid(self, s: str) -> bool:
        d = {'(':')','[':']','{':'}'}

        res = []
        for i in s:
            if res != [] and i == res[-1]:
                res.pop()
            else:
                try:
                    res.append(d[i])
                except:
                    return False 
        return res == []
#  1047. 删除字符串中的所有相邻重复项
    def removeDuplicates(self, s: str) -> str:
        res = []
        for i in s:
            if res and res[-1] == i:
                res.pop()
            else:
                res.append(i)

        return ''.join(res)
#  150. 逆波兰表达式求值
    def evalRPN(self, tokens: List[str]) -> int:
        res = []
        for i in tokens:
            if i == '+':
                res.append(res.pop() + res.pop())
            elif i == '-':
                res.append(-res.pop() + res.pop())
            elif i == '*':
                res.append(res.pop() * res.pop())
            elif i == '/':
                res.append(int(1/res.pop() * res.pop()))
            else:
                res.append(int(i))
        return res[-1]
                


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