华为OD机试-猴子爬山-dp（JAVA 2025A卷）

import java.util.Scanner;

public class Test {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while(sc.hasNextLine()){
            int n = sc.nextInt();
            // dp
            System.out.println(solve1(n));
            // double pointer
            System.out.println(solve2(n));
        }
    }

    private static int solve1(int n) {
        int[] dp = new int[n+1];
        // 初始化
        for(int i=0;i<3;i++){
            dp[i] = 1;
        }
        for(int i =3;i<=n;i++){
            dp[i] =dp[i-3]+dp[i-1];
        }
        return dp[n];
    }

    private static int solve2(int n) {
        int f1=1,f2=1,f3=2,f4 = 0;
        for(int i=4;i<=n;i++){
            f4=f3+f1;
            f1=f2;
            f2=f3;
            f3=f4;
        }
        return f4;
    }

}