BOJ 2579번 계단 오르기

package BOJ.DP;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

/**
 * BOJ 2579
 * https://www.acmicpc.net/problem/2579
 */
public class BOJ_2579 {

    private static int[] arr;
    private static int[] answer;

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

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        int n = Integer.parseInt(br.readLine());
        arr = new int[n+1];
        answer = new int[n+1];
        for(int i=1; i<=n; i++){
            arr[i] = Integer.parseInt(br.readLine());
        }
        // D(n) : n번째 계단 밟는 최대 점수
        // n-1 밟는 경우 : D(n-3) + P(n-1) + P(n)
        // n-2 밟는 경우 : D(n-2) + P(n)
        // D(n) = max ( D(n-3) + P(n-1) + P(n), D(n-2) + P(n) )

        solve(n);
        System.out.println(answer[n]);
    }

    private static void solve(int n) {
        answer[1] = arr[1];
        answer[2] = arr[1] + arr[2];

        for(int i=3; i<=n; i++){
            answer[i] = Math.max(answer[i-3]+arr[i-1]+arr[i],answer[i-2]+arr[i]);
        }
    }
}