利用栈求解算术表达式的值，程序分为两种表达式，中缀式与后缀式，分别得用栈先入后出的特性，以及运算符的优先级比较，进行求解-use arithmetic to solve the value of the expression, procedures are divided into two expressions, and the sergeant-type suffix. Stack were starting after the first-in-the characteristics, a