算法评估preFIX EX pression？ [英] Algorithm to evaluate prefix expression?

问题描述

我有一个preFIX EX pression，只有拥有4个二进制运算符（+， - ，*，/）。一个直来评估这样一个前pression前进的方向是将其转换为后缀EX pression，然后评估该EX pression。但我在寻找一种算法，直接做到这一点，而不将其转换为任何其他前pression？

I have a prefix expression that only has the 4 binary operators(+,-,*,/) .A straight forward way to evaluate such an expression is to convert it to a postfix expression and then evaluate that expression. But I am looking for an algorithm that does this directly without converting it to any other expression ?

推荐答案

简单而又重复的：

Evaluate(input):
  Read a token from input.
  If the token is a value:
    Return the value of the token
  If the token is a binary operator:
    Let first_argument = Evaluate(input)
    Let second_argument = Evaluate(input)
    Return apply(operator, first_argument, second_argument)

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