105 lines
2.5 KiB
Java
105 lines
2.5 KiB
Java
// Java program to print top view of Binary tree
|
|
import java.util.*;
|
|
|
|
// Class for a tree node
|
|
class TreeNode
|
|
{
|
|
// Members
|
|
int key;
|
|
TreeNode left, right;
|
|
|
|
// Constructor
|
|
public TreeNode(int key)
|
|
{
|
|
this.key = key;
|
|
left = right = null;
|
|
}
|
|
}
|
|
|
|
// A class to represent a queue item. The queue is used to do Level
|
|
// order traversal. Every Queue item contains node and horizontal
|
|
// distance of node from root
|
|
class QItem
|
|
{
|
|
TreeNode node;
|
|
int hd;
|
|
public QItem(TreeNode n, int h)
|
|
{
|
|
node = n;
|
|
hd = h;
|
|
}
|
|
}
|
|
|
|
// Class for a Binary Tree
|
|
class Tree
|
|
{
|
|
TreeNode root;
|
|
|
|
// Constructors
|
|
public Tree() { root = null; }
|
|
public Tree(TreeNode n) { root = n; }
|
|
|
|
// This method prints nodes in top view of binary tree
|
|
public void printTopView()
|
|
{
|
|
// base case
|
|
if (root == null) { return; }
|
|
|
|
// Creates an empty hashset
|
|
HashSet<Integer> set = new HashSet<>();
|
|
|
|
// Create a queue and add root to it
|
|
Queue<QItem> Q = new LinkedList<QItem>();
|
|
Q.add(new QItem(root, 0)); // Horizontal distance of root is 0
|
|
|
|
// Standard BFS or level order traversal loop
|
|
while (!Q.isEmpty())
|
|
{
|
|
// Remove the front item and get its details
|
|
QItem qi = Q.remove();
|
|
int hd = qi.hd;
|
|
TreeNode n = qi.node;
|
|
|
|
// If this is the first node at its horizontal distance,
|
|
// then this node is in top view
|
|
if (!set.contains(hd))
|
|
{
|
|
set.add(hd);
|
|
System.out.print(n.key + " ");
|
|
}
|
|
|
|
// Enqueue left and right children of current node
|
|
if (n.left != null)
|
|
Q.add(new QItem(n.left, hd-1));
|
|
if (n.right != null)
|
|
Q.add(new QItem(n.right, hd+1));
|
|
}
|
|
}
|
|
}
|
|
|
|
// Driver class to test above methods
|
|
public class PrintTopViewofTree
|
|
{
|
|
public static void main(String[] args)
|
|
{
|
|
/* Create following Binary Tree
|
|
1
|
|
/ \
|
|
2 3
|
|
\
|
|
4
|
|
\
|
|
5
|
|
\
|
|
6*/
|
|
TreeNode root = new TreeNode(1);
|
|
root.left = new TreeNode(2);
|
|
root.right = new TreeNode(3);
|
|
root.left.right = new TreeNode(4);
|
|
root.left.right.right = new TreeNode(5);
|
|
root.left.right.right.right = new TreeNode(6);
|
|
Tree t = new Tree(root);
|
|
System.out.println("Following are nodes in top view of Binary Tree");
|
|
t.printTopView();
|
|
}
|
|
} |