if(subroot==NULL) return;
        if(a[x].first==0 || a[x].second>deep) 
            a[x]={subroot->data,deep};
        NLR(deep+1,subroot->left,a,x-1);
        NLR(deep+1,subroot->right,a,x+1);
    }
    void topView(Node * root) {
        if(root==NULL) return;
        map<int,pair<int,int>> res;
        int x=0;
        int deep=0;
        res[x]={root->data,deep};
        NLR(deep+1,root->left,res,x-1);
        NLR(deep+1,root->right,res,x+1);
        for(auto i:res){
            cout<<i.second.first<<" ";
        }
    }