编译原理词法分析器的功能是利用函数之间的递归调用模拟语法树自上而下的构造过程。 改造文法：消除二义性、消除左递归、提取左因子，判断是否为LL（1）文法 -Compiler theory lexical analyzer function is to use recursive function calls between the simulation process of constructing the syntax tree from the top down. Transforma

利用递归函数调用方式，将所输入的5个字符，以相反顺序打印出来。-Recursive function calls, five characters entered, printed out in reverse order

算法设计中重点的几个函数算法，含有递归、堆栈、背包等-Several function algorithm algorithm design focus, containing recursion, stack, backpacks, etc.

编写递归函数，求n个元素集合的所有子集。不妨令集合元素为小写字母，原集合为{‘a’, ‘b’, …, ‘a’ + n - 1}。-Write a recursive function, all subsets of a set of elements for n