题解 | 牛牛学数列5

import java.util.*;
public class Main{
    public static int res = 0;
    public static int[] flag = new int[50];
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        flag[1] = 1;
        flag[2] = 1;
        Main.dfs(47);
        System.out.println(flag[n]);
    }
    public static int dfs(int n){//求前n项斐波那契
        if(n==1||n==2){
            return 1;
        }
        if(flag[n]!=0){
            return flag[n];
        }
        res = dfs(n-1)+dfs(n-2);
        flag[n] = res;
        return res;
    }
}