括号匹配是栈的一种经典应用。本功能主要是实现输入一串字符（里面包括左括号右括号等），判断你的括号是否有相应的匹配值。如果没有则返回错误并退出程序。-bracket matching program is the typical application of stack. the program of it is to check whether the sequence have been right in the aspect of bracket.