Print all nodes between two given levels in Binary Tree

Given a binary tree, print all nodes between two given levels in a binary tree. Print the nodes level wise, i.e., the nodes for any level should be printed from left to right.

In the above tree, if starting level is 2 and ending level is 3 then solution should print:

2 3 
4 5 6 7 

Note: Level number starts with 1. That is, the root node is at level 1.

Prerequisite: Level order Traversal.

The idea is to do level order traversal of the tree using a queue and keep track of the current level. If the current level lies between the starting and ending level then print the nodes at that level.

Algorithm:

levelordertraverse (root, startLevel, endLevel)
q -> empty queue
q.enqueue (root)
level -> 0
while (not q.isEmpty())
     size -> q.size()
     level = level + 1
     while (size)
          node -> q.dequeue()
          if (level between startLevel and endevel)
               print (node)
           if(node.leftnull)
                q.enqueue (node. left)
           if(node.leftnull)
                q.enqueue(node.right)
           size =size -1

Below is the implementation of the above algorithm:

Java

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// Java program for Print all nodes
// between two given levels in
// a binary tree
  
import java.util.LinkedList;
import java.util.Queue;
  
public class BinaryTree {
  
    // Class containing left and right
    // child of current node and key value
    static class Node {
  
        int data;
        Node left, right;
  
        public Node(int item)
        {
            data = item;
            left = right = null;
        }
    }
  
    // Root of the Binary Tree
    Node root;
    public BinaryTree()
    {
        root = null;
    }
  
    // Iterative function to print all
    // nodes between two given
    // levels in a binary tree
    void printNodes(Node root, int start, int end)
    {
        if (root == null) {
            return;
        }
  
        // create an empty queue and
        // enqueue root node
        Queue<Node> queue = new LinkedList<Node>();
        queue.add(root);
  
        // pointer to store current node
        Node curr = null;
  
        // maintains level of current node
        int level = 0;
  
        // run till queue is not empty
        while (!queue.isEmpty()) {
            // increment level by 1
            level++;
  
            // calculate number of nodes in
            // current level
            int size = queue.size();
  
            // process every node of current level
            // and enqueue their non-empty left
            // and right child to queue
            while (size != 0) {
                curr = queue.peek();
                queue.poll();
  
                // print the node if its level is
                // between given levels
                if (level >= start && level <= end) {
                    System.out.print(curr.data + " ");
                }
                if (curr.left != null) {
                    queue.add(curr.left);
                }
  
                if (curr.right != null) {
                    queue.add(curr.right);
                }
                size--;
            }
  
            if (level >= start && level <= end) {
                System.out.println("");
            };
        }
    }
  
    // Driver Code
    public static void main(String args[])
    {
        BinaryTree tree = new BinaryTree();
        tree.root = new Node(1);
        tree.root.left = new Node(2);
        tree.root.right = new Node(3);
        tree.root.left.left = new Node(4);
        tree.root.left.right = new Node(5);
        tree.root.right.left = new Node(6);
        tree.root.right.right = new Node(7);
  
        /* Constructed binary tree is 
             
           /  \ 
          2    3 
         / \  / \
        4   5 6  7 */
  
        int start = 2, end = 3;
  
        tree.printNodes(tree.root, start, end);
    }
}

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Python3

# Python3 program for Print all nodes
# between two given levels in
# a binary tree

# Helper function that allocates a new
# node with the given data and None
# left and right poers.
class newNode:

# Construct to create a new node
def __init__(self, key):
self.data = key
self.left = None
self.right = None

# Iterative function to pr all
# nodes between two given
# levels in a binary tree
def prNodes(root, start, end):

if (root == None):
return

# create an empty queue and
# enqueue root node
q = []
q.append(root)

# poer to ste current node
curr = None

# maains level of current node
level = 0

# run till queue is not empty
while (len(q)):

# increment level by 1
level += 1

# calculate number of nodes in
# current level
size = len(q)

# process every node of current level
# and enqueue their non-empty left
# and right child to queue
while (size != 0) :
curr = q[0]
q.pop(0)

# pr the node if its level is
# between given levels
if (level >= start and level <= end) : print(curr.data, end = " ") if (curr.left != None) : q.append(curr.left) if (curr.right != None) : q.append(curr.right) size -= 1 if (level >= start and level <= end) : print("") # Driver Code if __name__ == '__main__': """ Let us create Binary Tree shown in above example """ root = newNode(1) root.left = newNode(2) root.left.left = newNode(4) root.left.right = newNode(5) root.right = newNode(3) root.right.right = newNode(7) root.right.left = newNode(6) start = 2 end = 3 prNodes(root, start, end) # This code is contributed by # Shubham Singh(SHUBHAMSINGH10) [tabbyending]

Output:

2 3 
4 5 6 7


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Strategy Path planning and Destination matters in success No need to worry about in between temporary failures

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Improved By : SHUBHAMSINGH10