<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:
    vector<int> ans;
    void targetToK(TreeNode* root, int k, int dist){
        if(root == nullptr) return ;

        if(dist == k) {
            cout<<root->val<<" ";
            ans.push_back(root->val);
            return ;
        } 

        targetToK(root->left, k, dist+1);
        targetToK(root->right, k, dist+1);
    }
    void childParent(TreeNode* root, unordered_map<TreeNode*, TreeNode*>& mp) { 
        if(root == nullptr) return ;
        if(root->left) mp[root->left]=root;
        if(root->right) mp[root->right]=root;

        childParent(root->left, mp);
        childParent(root->right, mp);
    }
    vector<int> distanceK(TreeNode* root, TreeNode* target, int k) {
        targetToK(target,k,0);
        unordered_map<TreeNode*, TreeNode*> childToParent;
        childParent(root,childToParent);
        
        TreeNode* c = target;
        TreeNode* p = childToParent[c];

        while(k--) {
            p = childToParent[c];
            if(p!=nullptr)
                if(p->left!=nullptr && p->left->val == c->val) {
                    p->left = nullptr;
                } else if(p->right!=nullptr && p->right->val == c->val) {
                    p->right = nullptr;
                }

            targetToK(p,k,0);
            c = p;
        }
        
        return ans;
    }
};
12800