[백준 2133] 타일 채우기 (JAVA)

https://www.acmicpc.net/problem/2133

2133번: 타일 채우기

 

n=2 -> 3

n=4 -> 11

n=6 -> 41

 

점화식 : arr[i]= arr[i-1]*4 - arr[i-2]

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

public class Main {

	public static void main(String[] args) throws NumberFormatException, IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		int num = Integer.parseInt(br.readLine());
		int[] arr = new int[30];
		arr[0] = 1; // 1
		arr[1] = 3; // 2
		arr[2] = 11; // 4
		if (num % 2 == 0) {
			for (int i = 3; i <= num / 2; i++) {
				arr[i] = arr[i-1] *4 - arr[i-2];
			}
			System.out.println(arr[num/2]);
		}
		else {
			System.out.println(0);
		}
		
	}

}