0841-keys-and-rooms.rb

# frozen_string_literal: true

# 841. Keys and Rooms
# https://leetcode.com/problems/keys-and-rooms
# Medium

=begin
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.

Example 1:
Input: rooms = [[1],[2],[3],[]]
Output: true
Explanation:
We visit room 0 and pick up key 1.
We then visit room 1 and pick up key 2.
We then visit room 2 and pick up key 3.
We then visit room 3.
Since we were able to visit every room, we return true.

Example 2:
Input: rooms = [[1,3],[3,0,1],[2],[0]]
Output: false
Explanation: We can not enter room number 2 since the only key that unlocks it is in that room.

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.
=end

# @param {Integer[][]} rooms
# @return {Boolean}
def can_visit_all_rooms(rooms)
  seen = [0] * rooms.count
  seen[0] = 1
  stack = rooms[0]

  until stack.empty?
    r = stack.pop
    seen[r] = 1
    rooms[r].each do |k|
     stack << k if seen[k] == 0
   end
  end

  seen.find { |r| r == 0 }.nil?
end

# **************** #
#       TEST       #
# **************** #

require "test/unit"
class Test_can_visit_all_rooms < Test::Unit::TestCase
  def test_
    assert_equal true, can_visit_all_rooms([[1], [2], [3], []])
    assert_equal false, can_visit_all_rooms([[1, 3], [3, 0, 1], [2], [0]])
  end
end