<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 {
public:
    
    bool node2Root(TreeNode* root, int data, vector<TreeNode*>&path) {
        if(root == NULL) return false;
        if(root->val == data) {
            path.push_back(root);
            return true;
        }
        bool filc = node2Root(root->left,data,path);
        if(filc) {
            path.push_back(root);
            return true;
        }
        bool firc = node2Root(root->right,data,path);
        if(firc) {
            path.push_back(root);
            return true;
        }
        return false;
    }

    void printKlevelsDown(TreeNode* node, int k, TreeNode* blocker, vector<int>&distance) {
        if(k<0 || node == NULL || node == blocker) {
            return;
        }
        if(k==0) {
            distance.push_back(node->val);
        }
        printKlevelsDown(node->left,k-1,blocker,distance);
        printKlevelsDown(node->right,k-1,blocker,distance);
    }

    vector<int> distanceK(TreeNode* root, TreeNode* target, int k) {
        vector<TreeNode*> path;
        vector<int> distance;
        node2Root(root,target->val,path);
        for(int i=0;i<path.size();i++) {
            printKlevelsDown(path[i],k-i,i==0 ? NULL : path[i-1],distance);
        }    
        return distance;
    }
};
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