Maximum Candies You Can Get from Boxes
<p>You have <code>n</code> boxes labeled from <code>0</code> to <code>n - 1</code>. You are given four arrays: <code>status</code>, <code>candies</code>, <code>keys</code>, and <code>containedBoxes</code> where:</p>

<ul>
	<li><code>status[i]</code> is <code>1</code> if the <code>i<sup>th</sup></code> box is open and <code>0</code> if the <code>i<sup>th</sup></code> box is closed,</li>
	<li><code>candies[i]</code> is the number of candies in the <code>i<sup>th</sup></code> box,</li>
	<li><code>keys[i]</code> is a list of the labels of the boxes you can open after opening the <code>i<sup>th</sup></code> box.</li>
	<li><code>containedBoxes[i]</code> is a list of the boxes you found inside the <code>i<sup>th</sup></code> box.</li>
</ul>

<p>You are given an integer array <code>initialBoxes</code> that contains the labels of the boxes you initially have. You can take all the candies in <strong>any open box</strong> and you can use the keys in it to open new boxes and you also can use the boxes you find in it.</p>

<p>Return <em>the maximum number of candies you can get following the rules above</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> status = [1,0,1,0], candies = [7,5,4,100], keys = [[],[],[1],[]], containedBoxes = [[1,2],[3],[],[]], initialBoxes = [0]
<strong>Output:</strong> 16
<strong>Explanation:</strong> You will be initially given box 0. You will find 7 candies in it and boxes 1 and 2.
Box 1 is closed and you do not have a key for it so you will open box 2. You will find 4 candies and a key to box 1 in box 2.
In box 1, you will find 5 candies and box 3 but you will not find a key to box 3 so box 3 will remain closed.
Total number of candies collected = 7 + 4 + 5 = 16 candy.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> status = [1,0,0,0,0,0], candies = [1,1,1,1,1,1], keys = [[1,2,3,4,5],[],[],[],[],[]], containedBoxes = [[1,2,3,4,5],[],[],[],[],[]], initialBoxes = [0]
<strong>Output:</strong> 6
<strong>Explanation:</strong> You have initially box 0. Opening it you can find boxes 1,2,3,4 and 5 and their keys.
The total number of candies will be 6.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>n == status.length == candies.length == keys.length == containedBoxes.length</code></li>
	<li><code>1 &lt;= n &lt;= 1000</code></li>
	<li><code>status[i]</code> is either <code>0</code> or <code>1</code>.</li>
	<li><code>1 &lt;= candies[i] &lt;= 1000</code></li>
	<li><code>0 &lt;= keys[i].length &lt;= n</code></li>
	<li><code>0 &lt;= keys[i][j] &lt; n</code></li>
	<li>All values of <code>keys[i]</code> are <strong>unique</strong>.</li>
	<li><code>0 &lt;= containedBoxes[i].length &lt;= n</code></li>
	<li><code>0 &lt;= containedBoxes[i][j] &lt; n</code></li>
	<li>All values of <code>containedBoxes[i]</code> are unique.</li>
	<li>Each box is contained in one box at most.</li>
	<li><code>0 &lt;= initialBoxes.length &lt;= n</code></li>
	<li><code>0 &lt;= initialBoxes[i] &lt; n</code></li>
</ul>
Breadth-First Search; Graph; Array
func maxCandies(status []int, candies []int, keys [][]int, containedBoxes [][]int, initialBoxes []int) (ans int) {
	q := []int{}
	has := make(map[int]bool)
	took := make(map[int]bool)
	for _, box := range initialBoxes {
		has[box] = true
		if status[box] == 1 {
			q = append(q, box)
			took[box] = true
			ans += candies[box]
		}
	}
	for len(q) > 0 {
		box := q[0]
		q = q[1:]
		for _, k := range keys[box] {
			if status[k] == 0 {
				status[k] = 1
				if has[k] && !took[k] {
					q = append(q, k)
					took[k] = true
					ans += candies[k]
				}
			}
		}
		for _, b := range containedBoxes[box] {
			has[b] = true
			if status[b] == 1 && !took[b] {
				q = append(q, b)
				took[b] = true
				ans += candies[b]
			}
		}
	}
	return
}
