<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:
    void bfs(TreeNode*root,vector<int>&ans,int k){
         queue<TreeNode*>q;
         q.push(root);
          int lvl=0;
          while(q.size()>0){
             int sz=q.size();
             for(int i=0;i<sz;i++){
                 TreeNode*t=q.front();
                 q.pop();
                 if(t->left)q.push(t->left);
                 if(t->right)q.push(t->right);
             }
             lvl++;
             if(lvl==k){
                while(q.size()>0){
                     ans.push_back(q.front()->val);
                     q.pop();
                }
                break;
             }
          }
    }

    bool convert(TreeNode*curr,TreeNode*parent,TreeNode*target){
         if(curr==NULL)return false;
         if(curr==target){
            curr->left=parent;
            return true;
         }
         bool fromleft=convert(curr->left,curr,target);
         bool fromright=convert(curr->right,curr,target);
         if(fromleft){
            curr->left=parent;
            return true;
         }
         else if(fromright){
            curr->right=parent;
            return true;
         }
         return false;
    }
     
    vector<int> distanceK(TreeNode* root, TreeNode* target, int k) {
        if(k==0)return{target->val};
        vector<int>ans;
        bfs(target,ans,k);
        if(target==root)return ans;

        target->left=NULL;
        target->right=NULL;
        convert(root,NULL,target);
        bfs(target,ans,k);
         
        return ans;
    }
};
12000