编译原理小程序 有点小问题 源程序文件内容如下： main() { int a, b a = 10 　　 b = a + 20 } 要求输出如下： (2，”main”) (5，”（”） (5，”)”) (5，”{“} (1，”int”) (2，”a”) (5，”,”) (2，”b”) (5，” ”) (2，”a”) (4，”=”) (3，10) (5，” ”) (2，”b”) (4，”=”) (2，”a”) (4，”+”) (3，20) (5，” ”) (5，”)”)-Compiler Principle small programs have a small problem source files as follows : main () (int a, b a = b = a 10 20) output requirements are as follows : (2, "main") (5 ,"(") (5, " ) ") (5 ,"{"} (1," int ") (2," a ") (5 ,",") (2," b ") (5," ") (2," a " ) (4 ,"=") (3,10) (5, "") (2, "b") (4 ,"=") (2, "a") (4, "") (3,20 ) (5, "") (5 ,")")