백준 동적계획법 - 2579번 : 계단 오르기

https://www.acmicpc.net/problem/2579

2579번: 계단 오르기

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import java.io.*;
import java.util.*;

public class Main {
	public static void main(String[] args) throws IOException{
		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
		StringTokenizer st;
		
		st = new StringTokenizer(br.readLine());
		int n = Integer.parseInt(st.nextToken());
		int[] stair = new int[n+1];
		int[] memo = new int[n+1];
		for(int i=1; i<=n; i++) {
			st = new StringTokenizer(br.readLine());
			stair[i] = Integer.parseInt(st.nextToken());
		}
		memo[1] = stair[1];

		if(n>=2) {
			memo[2] = stair[2]+stair[1];
			if(n>=3) {
				memo[3] = Math.max(stair[2], stair[1])+stair[3];
				if(n>=4) {
					for(int i=4; i<=n; i++) {
						memo[i] = Math.max(memo[i-3]+stair[i-1], memo[i-2])+stair[i];
					}
				}
			}
		}
		bw.write(memo[n]+"");
		bw.close();
	}
}