python实现leetcode之150. 逆波兰表达式求值

解题思路

使用栈

150. 逆波兰表达式求值

代码

class Solution:
    def evalRPN(self, tokens: List[str]) -> int:
        stack = []
        for tok in tokens:
            if tok in '+-*/':
                second, first = stack.pop(), stack.pop()
                if tok == '+': stack.append(first+second)
                if tok == '-': stack.append(first-second)
                if tok == '*': stack.append(first*second)
                if tok == '/': stack.append(int(first/second))
            else:
                stack.append(int(tok))
        return stack[0]