Programmers_131130.java

package programmers.lv2;

import java.util.ArrayList;
import java.util.Comparator;

public class Programmers_131130 {
    public static void main(String[] args) {
        Programmers_131130 test = new Programmers_131130();
        int[] cards = { 8, 6, 3, 7, 2, 5, 1, 4 };
        int result = test.solution(cards);
        System.out.println("result: " + result);
    }

    boolean[] visited;

    public int solution(int[] cards) {
        visited = new boolean[cards.length];
        ArrayList<Integer> list = new ArrayList<>();
        for (int i = 0; i < cards.length; i++) {
            int idx = cards[i] - 1;
            if (!visited[idx]) {
                int size = dfs(idx, cards);
                list.add(size);
            }
        }
        list.sort(Comparator.reverseOrder());
        System.out.println(list.toString());

        int answer = 0;
        if (list.size() > 1) {
            answer = list.get(0) * list.get(1);
        }
        return answer;
    }

    public int dfs(int idx, int[] cards) {
        visited[idx] = true;
        int newIdx = cards[idx] - 1;
        if (!visited[newIdx]) {
            return 1 + dfs(newIdx, cards);
        }
        return 1;
    }
}