TopViewOfBinaryTree

class Q
{
    Node temp;
    int hd;
    Q(Node t, int h)
    {
        temp = t;
        hd = h;
    }
}
class View
{
    // function should print the topView of the binary tree
    static void topView(Node root)
    {
        HashMap<Integer, Integer> hm = new HashMap<Integer, Integer>();
        if(root == null)
            return;
        Queue<Q> q = new LinkedList<Q>();
        q.add(new Q(root, 0));
        int min = Integer.MAX_VALUE, max = Integer.MIN_VALUE;
        while(!q.isEmpty())
        {
            Q obj = q.poll();
            if(hm.get(obj.hd) == null)
                hm.put(obj.hd, obj.temp.data);
            
            if(obj.temp.left != null)
                q.add(new Q(obj.temp.left, obj.hd-1));
            if(obj.temp.right != null)
                q.add(new Q(obj.temp.right, obj.hd+1));
            if(obj.hd < min)
                min = obj.hd;
            if(obj.hd > max)
                max = obj.hd;
        }
        
        for(int i=min ; i<=max ; i++)
        {
            System.out.print(hm.get(i) + " ");
        }
    }