表达式求值***

将中缀表达式转换为后缀表达式。假设输入的算法表达式的运算符只有“＋、－、×、/、（、）”这几种。

要求：用栈完成；首先要判断输入的表达式括号是否配对，在正确表达式的基础上转换为后缀表达式，然后计算结果。

-*** Expression evaluation will be converted to postfix infix expression expression. Assume that the input of the algorithm expression of only " +,-,×,/,(,)"　these types of operators. Requirements: completion of the stack　we must first determine whether the pair enter the expression in brackets in the right on the basis of the expression into postfix expression, then calculate the results.