任务 编写程序计算波兰表达式的值。 输入 输入第一行是一个整数，表示输入文件中共有几个波兰式，之后每一行是一个波兰表达式。 -Enter the first line is an integer, the input file there are several Polish, followed by a Polish expression for each line. Each expression contains numbers and binary operators+