题解 | #后缀表达式求值#

#
# 
# @param tokens string字符串一维数组 
# @return int整型
#
from collections import deque
class Solution:
    def evalRPN(self , tokens ):
        # write code here
        n = deque()
        for i in tokens:
            if i == '+' or i == '-' or i == '*' or i == '/':
                n1 = n.pop()
                n2 = n.pop()
                if i == '+':
                    num1 = n1 + n2
                elif i == '-':
                    num1 = n2 - n1
                elif i == '*':
                    num1 = n1 * n2
                else:
                    num1 = n2 / n1
                n.append(num1)
            else:
                n.append(int(i))
        return n.pop()