FJ的字符串

规律如下：

f(A1)=A;

f(A2)=f(A1)+B+f(A1);

f(A3)=f(A2)+C+f(A2);

f(A4)=f(A3)+D+f(A3);

依此类推·····

import java.util.Scanner;

public class Fj{
	
	private static char [] c={'A','B','C','D','E','F','G','H','I','J','K','L','M',
			          'N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};

	public static void main(String[] args) {
		 
		Scanner scan=new Scanner(System.in);
		
		int n=scan.nextInt();
		
		f(n);
		
	}
	
	private static void f(int n){
		
		if(n==1){
			
			System.out.print("A");
			
		}else{
			
			f(n-1);
			System.out.print(c[n-1]);
			f(n-1);
		}
	}
}