<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.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
    private:
        void buildGraph(TreeNode* root, unordered_map<int, vector<int>>& adj, TreeNode* parent = nullptr) {
    if (!root) return;

    if (parent) {
        cout << "1st  " << parent->val << " " << root->val <<endl;
        adj[root->val].push_back(parent->val);
        adj[parent->val].push_back(root->val);
    }

    buildGraph(root->left, adj, root);
    buildGraph(root->right, adj, root);
}

void printAdjacencyList(const unordered_map<int, vector<int>>& adj) {
    for (const auto& pair : adj) {
        cout << "Node " << pair.first << ": ";
        for (int neighbor : pair.second) {
            cout << neighbor << " ";
        }
        cout << endl;
    }
}
public:
    vector<int> distanceK(TreeNode* root, TreeNode* target, int k) {
        unordered_map<int, vector<int>>adj;
        buildGraph(root,adj);
        unordered_map<int,int>dist;
        vector<int>ans;
        vector<int>farzi;
        farzi.push_back(target->val);
        if(k==0) return farzi;
        queue<int>q;
        q.push(target->val);
        dist[target->val]=0;
        while(!q.empty()){
            for (int i = 0; i < q.size(); i++) {
                int node = q.front();
                q.pop();
                for(int n:adj[node]){
                    if (dist.find(n) == dist.end())
                    {
                        dist[n]=dist[node]+1;
                        if(dist[n]==k)
                        {
                            ans.push_back(n);
                        }
                        else{
                            q.push(n);
                        }
                    }
                }
            }
        }
        return ans;
    }
};
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