题目：

题解：

class Solution:def evalRPN(self, tokens: List[str]) -> int:op_to_binary_fn = {"+": add,"-": sub,"*": mul,"/": lambda x, y: int(x / y),   # 需要注意 python 中负数除法的表现与题目不一致}n = len(tokens)stack = [0] * ((n + 1) // 2)index = -1for token in tokens:try:num = int(token)index += 1stack[index] = numexcept ValueError:index -= 1stack[index] = op_to_binary_fn[token](stack[index], stack[index + 1])return stack[0]