/*
Keys and Rooms

Instructions:
There are n rooms labeled from 0 to n - 1 and all the rooms are locked except for room 0. Your goal is to visit all the rooms. However, you cannot enter a locked room without having its key.

When you visit a room, you may find a set of distinct keys in it. Each key has a number on it, denoting which room it unlocks, and you can take all of them with you to unlock the other rooms.

Given an array rooms where rooms[i] is the set of keys that you can obtain if you visited room i, return true if you can visit all the rooms, or false otherwise.

Constraints:
n == rooms.length
2 <= n <= 1000
0 <= rooms[i].length <= 1000
1 <= sum(rooms[i].length) <= 3000
0 <= rooms[i][j] < n
All the values of rooms[i] are unique.
*/
package main

import "fmt"

func main() {
	res := canVisitAllRooms([][]int{{1}, {2}, {3}, {}})
	fmt.Printf("Example 1 works: %+v\n\n", res)

	res = canVisitAllRooms([][]int{{1, 3}, {3, 0, 1}, {2}, {0}})
	fmt.Printf("Example 2 works: %+v\n", res)
}

func canVisitAllRooms(rooms [][]int) bool {
	if len(rooms) > 0 && len(rooms[0]) == 0 {
		return false
	}

	keys := getAllKeys(0, make(map[int]struct{}), rooms)
	keys[0] = struct{}{}

	for i := 0; i < len(rooms); i++ {
		if _, ok := keys[i]; !ok {
			return false
		}
	}
	return true
}

func getAllKeys(index int, seen map[int]struct{}, rooms [][]int) map[int]struct{} {
	keys := map[int]struct{}{}

	for j := 0; j < len(rooms[index]); j++ {
		if _, ok := seen[rooms[index][j]]; ok {
			continue
		} else {
			seen[rooms[index][j]] = struct{}{}
		}
		keys[rooms[index][j]] = struct{}{}
		insideKeys := getAllKeys(rooms[index][j], seen, rooms)
		for k := range insideKeys {
			keys[k] = struct{}{}
		}
	}

	return keys
}