访问完所有房间的第一天

/*
思路:
1. 使用Java Stream流的方式来解决该问题。
2. 使用一个数组来记录每个房间的访问次数，通过Stream处理来决定下一个房间。
*/

import java.util.stream.IntStream;

public class VisitRoomsStream {
    public int firstDayToVisitAllRooms(int[] nextVisit) {
        int n = nextVisit.length;
        int[] visitCount = new int[n];
        int[] current = new int[]{0}; // 当前位置初始化为房间0
        long[] currentDay = new long[]{0};
        boolean[] visited = new boolean[n];

        IntStream.iterate(0, i -> visited[i] ? -1 : current[0]).filter(i -> i != -1).forEach(i -> {
            if (visitCount[current[0]] == 0) {
                visited[current[0]] = true;
            }
            visitCount[current[0]]++;
            currentDay[0]++;

            if (visitCount[current[0]] % 2 == 1) {
                current[0] = nextVisit[current[0]];
            } else {
                current[0] = (current[0] + 1) % n;
            }
        });

        return (int) (currentDay[0] % (1e9 + 7));
    }

    public static void main(String[] args) {
        VisitRoomsStream vr = new VisitRoomsStream();
        int[] nextVisit = {0, 0, 2};
        System.out.println(vr.firstDayToVisitAllRooms(nextVisit)); // 输出 6
    }
}