Day-16

 vector<int> verticalOrder(Node *root)
    {
        //Your code here
         //Your code here
       vector <int> res;
        //creating a map to store nodes at a particular horizontal distance.
        map<int,vector<int>>mp;
        
        //creating empty queue for level order traversal.
        queue<pair<Node*,int>>q;
        q.push({root,0});
        
        while(!q.empty())
        {
            pair<Node*,int> temp=q.front();
            Node* temp_root=temp.first;
            int distance=temp.second;
            mp[distance].push_back(temp_root->data);
            q.pop();
            
            //if left child of temp_root exists, pushing it in
            //the queue with the horizontal distance.
            if(temp_root->left)
            {
                q.push({temp_root->left,distance-1});
            }
            //if right child of temp_root exists, pushing it in
            //the queue with the horizontal distance.
            if(temp_root->right)
            {
                q.push({temp_root->right,distance+1});
            }
        }
        
        //traversing the map and storing the nodes in list 
        //at every horizontal distance.
        for(auto it=mp.begin();it!=mp.end();it++)
        {
            vector<int> ans=it->second;
            
            for(auto x:ans)
                res.push_back (x);
        }
        //returning the output list.
        return res;
    }