本文共 1044 字，大约阅读时间需要 3 分钟。

Evaluate the value of an arithmetic expression in Reverse Polish Notation.

Valid operators are +, -, *, /. Each operand may be an integer or another expression.

Some examples:

python

class Solution(object):    def isOp(self,s):        return s=="+" or s=="-" or s=="*" or s=="/"    def add(self,op1,op2):        return op1+op2    def sub(self,op1,op2):        return op1-op2    def mul(self,op1,op2):        return op1 * op2    def div(self,op1,op2):        if op1*op2<0:            return -((-op1)/op2)        return op1/op2    operator = {
  "+":add,"-":sub,"*":mul,"/":div}    def evalRPN(self,tokens):        nums=[]        for s in tokens:            if self.isOp(s):                op2 = nums.pop()                op1 = nums.pop()                re = self.operator.get(s)(self,op1,op2)                nums.append(re)            else:                nums.append(int(s))        return nums[0]

转载地址：http://uwqmi.baihongyu.com/