Committing BinaryTree.java

BinaryTree.java

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+// Java program to print top
+// view of binary tree
+import java.util.LinkedList;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.Queue;
+import java.util.TreeMap;
+
+// class to create a node
+class Node {
+	int data;
+	Node left, right;
+
+	public Node(int data)
+	{
+		this.data = data;
+		left = right = null;
+	}
+}
+
+// class of binary tree
+class BinaryTree {
+	Node root;
+
+	public BinaryTree() { root = null; }
+
+	// function should print the topView of
+	// the binary tree
+	private void TopView(Node root)
+	{
+		class QueueObj {
+			Node node;
+			int hd;
+
+			QueueObj(Node node, int hd)
+			{
+				this.node = node;
+				this.hd = hd;
+			}
+		}
+		Queue<QueueObj> q = new LinkedList<QueueObj>();
+		Map<Integer, Node> topViewMap
+			= new TreeMap<Integer, Node>();
+
+		if (root == null) {
+			return;
+		}
+		else {
+			q.add(new QueueObj(root, 0));
+		}
+
+		System.out.println(
+			"The top view of the tree is : ");
+
+		// count function returns 1 if the container
+		// contains an element whose key is equivalent
+		// to hd, or returns zero otherwise.
+		while (!q.isEmpty()) {
+			QueueObj tmpNode = q.poll();
+			if (!topViewMap.containsKey(tmpNode.hd)) {
+				topViewMap.put(tmpNode.hd, tmpNode.node);
+			}
+
+			if (tmpNode.node.left != null) {
+				q.add(new QueueObj(tmpNode.node.left,
+								tmpNode.hd - 1));
+			}
+			if (tmpNode.node.right != null) {
+				q.add(new QueueObj(tmpNode.node.right,
+								tmpNode.hd + 1));
+			}
+		}
+		for (Entry<Integer, Node> entry :
+			topViewMap.entrySet()) {
+			System.out.print(entry.getValue().data);
+		}
+	}
+
+	// Driver Program to test above functions
+	public static void main(String[] args)
+	{
+		/* Create following Binary Tree
+			1
+		/ \
+		2 3
+		\
+			4
+			\
+			5
+			\
+				6*/
+		BinaryTree tree = new BinaryTree();
+		tree.root = new Node(1);
+		tree.root.left = new Node(2);
+		tree.root.right = new Node(3);
+		tree.root.left.right = new Node(4);
+		tree.root.left.right.right = new Node(5);
+		tree.root.left.right.right.right = new Node(6);
+		System.out.println(
+			"Following are nodes in top view of Binary Tree");
+		tree.TopView(tree.root);
+	}
+}