题解 | #有多少个不同的二叉搜索树#

import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int nodeNum = scan.nextInt();
        System.out.println(getTotal(nodeNum));
    }
    public static int getTotal(int num){
        if (num <= 1){
            return 1;
        }
        int res = 0;
        for (int i = 1; i <= num; i++) {
            res += getTotal(i - 1) * getTotal(num - i);
        }
        return res;
    }
}