# coding=utf-8

"""

@project : algorithmPython

@ide : PyCharm

@file : evalRPN

@author : illusion

@desc : 150. 逆波兰表达式求值 https://leetcode-cn.com/problems/evaluate-reverse-polish-notation/

@create : 2021/5/27 1:22 下午:54

"""

from typing import List

class Solution:

def evalRPN(self, tokens: List[str]) -> int:

stack = []

for token in tokens:

if token != '+' and token != '-' and token != '*' and token != '/':

stack.append(int(token))

continue

if len(stack) < 2:

continue

n2 = stack.pop()

n1 = stack.pop()

if token == '+':

stack.append(n1 + n2)

elif token == '-':

stack.append(n1 - n2)

elif token == '*':

stack.append(n1 * n2)

elif token == '/':

stack.append(int(n1 / n2))

return stack.pop()

if __name__ == "__main__":

s = Solution()

print(s.evalRPN(["10", "6", "9", "3", "+", "-11", "*", "/", "*", "17", "+", "5", "+"]))