Leetcode 150逆波兰表达式求值

yeah_panda

于 2020-08-15 18:02:16 发布

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分类专栏： Leetcode 文章标签： stack leetcode 栈 python 算法

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150逆波兰表达式求值

class Solution(object):
    def evalRPN(self, tokens):
        """
        :type tokens: List[str]
        :rtype: int
        """
        stack =[]
        for token in tokens:
            if token not in '+-*/':
                stack.append(token)
            else:
                right_num = int(stack.pop())
                left_num = int(stack.pop())
                if token == '+':
                    result = left_num + right_num
                elif token == '-':
                    result = left_num - right_num
                elif token == '*':
                    result = left_num * right_num
                elif token == '/':
                    result = int(left_num / right_num)
                stack.append(str(result))
        return int(stack[-1])