<p>Given the <code>root</code> of a binary tree, the value of a target node <code>target</code>, and an integer <code>k</code>, return <em>an array of the values of all nodes that have a distance </em><code>k</code><em> from the target node.</em></p>

<p>You can return the answer in <strong>any order</strong>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://s3-lc-upload.s3.amazonaws.com/uploads/2018/06/28/sketch0.png" style="width: 500px; height: 429px;" />
<pre>
<strong>Input:</strong> root = [3,5,1,6,2,0,8,null,null,7,4], target = 5, k = 2
<strong>Output:</strong> [7,4,1]
Explanation: The nodes that are a distance 2 from the target node (with value 5) have values 7, 4, and 1.
</pre>

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

<pre>
<strong>Input:</strong> root = [1], target = 1, k = 3
<strong>Output:</strong> []
</pre>

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

<ul>
	<li>The number of nodes in the tree is in the range <code>[1, 500]</code>.</li>
	<li><code>0 &lt;= Node.val &lt;= 500</code></li>
	<li>All the values <code>Node.val</code> are <strong>unique</strong>.</li>
	<li><code>target</code> is the value of one of the nodes in the tree.</li>
	<li><code>0 &lt;= k &lt;= 1000</code></li>
</ul>

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
def solve(root, target, k):
    dist = {}
    find(root, dist, target)
    res = []
    traverse(root, 0, res, dist, target, k)
    return res

def find(root, dist, target):
    if root is None:
        return -1
    if root == target:
        dist[root] = 0
        return 0
    left = find(root.left, dist, target)
    if left >= 0:
        dist[root] = left + 1
        return left + 1
    right = find(root.right, dist, target)
    if right >= 0:
        dist[root] = right + 1
        return right + 1
    return -1

def traverse(root, length, res, dist, target, k):
    if root is None:
        return
    if root in dist:
        length = dist[root]    
    if length == k:
        res.append(root.val)
    traverse(root.left, length + 1, res, dist, target, k)
    traverse(root.right, length + 1, res, dist, target, k)

class Solution:
    def distanceK(self, root: TreeNode, target: TreeNode, k: int) -> List[int]:
        return solve(root, target, k)
16500