四则运算主要是用字符串形式接收一个带括号的四则运算表达式，然后按照四则运算优先级的算法先括号，后乘方，乘除，加减这样的顺序将这个算式解出。-Arithmetic is mainly used to receive a string of four operations with the expression in parentheses, and then follow the four operations in parentheses first priority of the algorithm, after involution, multiplication and division, addition and subtraction in this order to solve this formula.