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bottom-view-binary-tree.java
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120 lines (102 loc) · 3.43 KB
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// Java Program to print Bottom View of Binary Tree
import java.util.*;
import java.util.Map.Entry;
// Tree node class
class Node
{
int data; //data of the node
int hd; //horizontal distance of the node
Node left, right; //left and right references
// Constructor of tree node
public Node(int key)
{
data = key;
hd = Integer.MAX_VALUE;
left = right = null;
}
}
//Tree class
class Tree
{
Node root; //root node of tree
// Default constructor
public Tree() {}
// Parameterized tree constructor
public Tree(Node node)
{
root = node;
}
// Method that prints the bottom view.
public void bottomView()
{
if (root == null)
return;
// Initialize a variable 'hd' with 0 for the root element.
int hd = 0;
// TreeMap which stores key value pair sorted on key value
Map<Integer, Integer> map = new TreeMap<>();
// Queue to store tree nodes in level order traversal
Queue<Node> queue = new LinkedList<Node>();
// Assign initialized horizontal distance value to root
// node and add it to the queue.
root.hd = hd;
queue.add(root);
// Loop until the queue is empty (standard level order loop)
while (!queue.isEmpty())
{
Node temp = queue.remove();
// Extract the horizontal distance value from the
// dequeued tree node.
hd = temp.hd;
// Put the dequeued tree node to TreeMap having key
// as horizontal distance. Every time we find a node
// having same horizontal distance we need to replace
// the data in the map.
map.put(hd, temp.data);
// If the dequeued node has a left child add it to the
// queue with a horizontal distance hd-1.
if (temp.left != null)
{
temp.left.hd = hd-1;
queue.add(temp.left);
}
// If the dequeued node has a left child add it to the
// queue with a horizontal distance hd+1.
if (temp.right != null)
{
temp.right.hd = hd+1;
queue.add(temp.right);
}
}
// Extract the entries of map into a set to traverse
// an iterator over that.
Set<Entry<Integer, Integer>> set = map.entrySet();
// Make an iterator
Iterator<Entry<Integer, Integer>> iterator = set.iterator();
// Traverse the map elements using the iterator.
while (iterator.hasNext())
{
Map.Entry<Integer, Integer> me = iterator.next();
System.out.print(me.getValue()+" ");
}
}
}
// Main driver class
public class BottomView
{
public static void main(String[] args)
{
Node root = new Node(20);
root.left = new Node(8);
root.right = new Node(22);
root.left.left = new Node(5);
root.left.right = new Node(3);
root.right.left = new Node(4);
root.right.right = new Node(25);
root.left.right.left = new Node(10);
root.left.right.right = new Node(14);
Tree tree = new Tree(root);
System.out.println("Bottom view of the given binary tree:");
tree.bottomView();
}
}