백준 2579번

원본 : www.acmicpc.net/problem/2579

2579번: 계단 오르기

 

풀이

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;

public class Main {

	public static BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
	public static BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(System.out));

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

		int n = Integer.parseInt(reader.readLine());
		int input[] = new int[n];
		int calculate[] = new int[n];
		for (int i = 0; i < n; i++) {
			input[i] = Integer.parseInt(reader.readLine());
			calculate[i] = input[i];
		}

		if (n == 1) {
			writer.write(input[0] + "");
		} else if (n == 2) {
			writer.write(input[1] + input[0] + "");
		} else if (n == 3) {
			writer.write(maxValue(input[2] + input[1], input[2] + input[0]) + "");
		} else {
			calculate[1] += calculate[0];
			calculate[2] = maxValue(input[2] + input[0], input[2] + input[1]);

			for (int i = 3; i < n; i++) {
				calculate[i] = input[i] + maxValue(input[i - 1] + calculate[i - 3], calculate[i - 2]);
			}

			writer.write(calculate[calculate.length - 1] + "");
		}

		writer.flush();
	}

	public static int maxValue(int a, int b) {
		if (a >= b) {
			return a;
		} else {
			return b;
		}
	}

}