题目:
思路:递归
import java.util.Scanner;
public class Main{
public static void main(String[] args) {
Scanner in=new Scanner(System.in);
int n=in.nextInt();
System.out.println(f(n));
}
static String f(int n) {
if(n==1) {
return "A";
}
return f(n-1)+(char)('A'+n-1)+f(n-1);
}
}