蓝桥杯Sine之舞-简单易懂双层递归(JAVA)

解题思路:
先通过递归求An，再通过递归求Sn
注意事项:
设一个全局变量
参考代码:

import java.io.IOException;

import java.io.InputStreamReader;

import java.io.OutputStreamWriter;

import java.util.Scanner;

public class Main {

static int n;

static int i = n;

static Scanner sc = new Scanner(new InputStreamReader(System.in));

    static OutputStreamWriter out = new OutputStreamWriter(System.out);

public static void main(String[] args) throws Exception  {

Main.n = sc.nextInt();

Main.i = Main.n;

out.write(dfs(n));

        out.flush();

    }

public static String bfs(int n){  //求An

if(n==1) return "sin(1";

if((n&1)==0) return bfs(n-1)+"-sin("+n;

else return bfs(n-1)+"+sin("+n;

}

public static String dfs(int n){   //求Sn

if(n==1){

String s = bfs(1)+")";

return s+"+"+i;

}

String s = bfs(n);

String s1 = bfs(n);

while(s.contains("(")){

s = s.substring(s.indexOf("(")+1, s.length());

s1 += ")";

}

return "("+dfs(n-1)+")"+s1+"+"+ --Main.i;

}

}