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Print all the nodes except the leftmost node in every level of the given binary tree

Given a binary tree, the task is to print all the nodes except the leftmost in every level of the tree. The root is considered at level 0, and left most node of any level is considered as a node at position 0.

Examples: 

Input:
          1
       /     \
      2       3
    /   \       \
   4     5       6
        /  \
       7    8
      /      \
     9        10

Output:
3
5  6
8
10

Input:
          1
        /   \
       2     3
        \     \
         4     5
Output:
3
5

Approach: To print nodes level by level, use level order traversal. The idea is based on Print level order traversal line by line. For that, traverse nodes level by level and mark leftmost flag true just before the processing of each level and mark it false just after processing of the first node at each level.

Below is the implementation of the above approach:  




// C++ implementation of the approach
#include <bits/stdc++.h>
using namespace std;
 
// Structure of the tree node
struct Node {
    int data;
    Node *left, *right;
};
 
// Utility method to create a node
struct Node* newNode(int data)
{
    struct Node* node = new Node;
    node->data = data;
    node->left = node->right = NULL;
    return (node);
}
 
// Function to print all the nodes
// except the leftmost in every level
// of the given binary tree
// with level order traversal
void excludeLeftmost(Node* root)
{
    // Base Case
    if (root == NULL)
        return;
 
    // Create an empty queue for level
    // order traversal
    queue<Node*> q;
 
    // Enqueue root
    q.push(root);
 
    while (1) {
 
        // nodeCount (queue size) indicates
        // number of nodes at current level.
        int nodeCount = q.size();
        if (nodeCount == 0)
            break;
 
        // Initialize leftmost as true
        // just before the beginning
        // of each level
        bool leftmost = true;
 
        // Dequeue all nodes of current level
        // and Enqueue all nodes of next level
        while (nodeCount > 0) {
            Node* node = q.front();
 
            // Switch leftmost flag after processing
            // the leftmost node
            if (leftmost)
                leftmost = !leftmost;
 
            // Print all the nodes except leftmost
            else
                cout << node->data << " ";
            q.pop();
            if (node->left != NULL)
                q.push(node->left);
            if (node->right != NULL)
                q.push(node->right);
            nodeCount--;
        }
        cout << "\n";
    }
}
 
// Driver code
int main()
{
    struct Node* root = newNode(1);
    root->left = newNode(2);
    root->right = newNode(3);
    root->left->left = newNode(4);
    root->left->right = newNode(5);
    root->right->left = newNode(6);
    root->right->right = newNode(7);
    root->left->right->left = newNode(8);
    root->left->right->right = newNode(9);
    root->left->right->right->right = newNode(10);
 
    excludeLeftmost(root);
 
    return 0;
}
 





                        























                                    



                                    




                                    




                                    


                                



















// Java implementation of the approach 



import java.util.*;



 



class Sol



{



     


// Structure of the tree node 



static class Node 



{ 



    int data; 




    Node left, right; 



}; 


 


// Utility method to create a node 



static Node newNode(int data) 



{ 



    Node node = new Node(); 




    node.data = data; 




    node.left = node.right = null; 




    return (node); 



} 


 


// Function to print all the nodes 


// except the leftmost in every level 


// of the given binary tree 


// with level order traversal 



static void excludeLeftmost(Node root) 



{ 



    // Base Case 




    if (root == null) 




        return; 



 



    // Create an empty queue for level 




    // order traversal 




    Queue<Node> q = new LinkedList<Node>(); 



 



    // Enqueue root 




    q.add(root); 



 



    while (true) 




    { 



 



        // nodeCount (queue size) indicates 




        // number of nodes at current level. 




        int nodeCount = q.size(); 




        if (nodeCount == 0) 




            break; 



 



        // Initialize leftmost as true 




        // just before the beginning 




        // of each level 




        boolean leftmost = true; 



 



        // Dequeue all nodes of current level 




        // and Enqueue all nodes of next level 




        while (nodeCount > 0)




        { 




            Node node = q.peek(); 



 



            // Switch leftmost flag after processing 




            // the leftmost node 




            if (leftmost) 




                leftmost = !leftmost; 



 



            // Print all the nodes except leftmost 




            else




                System.out.print( node.data + " "); 




            q.remove(); 




            if (node.left != null) 




                q.add(node.left); 




            if (node.right != null) 




                q.add(node.right); 




            nodeCount--; 




        } 




        System.out.println(); 




    } 



} 


 


// Driver code 



public static void main(String args[])



{ 



    Node root = newNode(1); 




    root.left = newNode(2); 




    root.right = newNode(3); 




    root.left.left = newNode(4); 




    root.left.right = newNode(5); 




    root.right.left = newNode(6); 




    root.right.right = newNode(7); 




    root.left.right.left = newNode(8); 




    root.left.right.right = newNode(9); 




    root.left.right.right.right = newNode(10); 



 



    excludeLeftmost(root); 



}


} 


 


// This code is contributed by Arnab Kundu


















                        






                        























                                    



                                    




                                    




                                    


                                



















# Python implementation of the approach



from collections import dequeue



# Structure of the tree node



class Node:




    def __init__(self):




        self.data = 0




        self.left = None




        self.right = None



 


# Utility method to create a node



def newNode(data: int) -> Node:




    node = Node()




    node.data = data




    node.left = None




    node.right = None




    return node



 


# Function to print all the nodes


# except the leftmost in every level


# of the given binary tree


# with level order traversal



def excludeLeftMost(root: Node):



 



    # Base Case




    if root is None:




        return



 



    # Create an empty queue for level




    # order traversal




    q = dequeue()



 



    # Enqueue root




    q.append(root)



 



    while 1:



 



        # nodeCount (queue size) indicates




        # number of nodes at current level




        nodeCount = len(q)




        if nodeCount == 0:




            break



 



        # Initialize leftmost as true




        # just before the beginning




        # of each level




        leftmost = True



 



        # Dequeue all nodes of current level




        # and Enqueue all nodes of next level




        while nodeCount > 0:




            node = q[0]



 



            # Switch leftmost flag after processing




            # the leftmost node




            if leftmost:




                leftmost = not leftmost



 



            # Print all the nodes except leftmost




            else:




                print(node.data, end=" ")




            q.popleft()



 



            if node.left is not None:




                q.append(node.left)




            if node.right is not None:




                q.append(node.right)




            nodeCount -= 1




        print()



 


# Driver Code



if __name__ == "__main__":




    root = Node()




    root = newNode(1)




    root.left = newNode(2)




    root.right = newNode(3)




    root.left.left = newNode(4)




    root.left.right = newNode(5)




    root.right.left = newNode(6)




    root.right.right = newNode(7)




    root.left.right.left = newNode(8)




    root.left.right.right = newNode(9)




    root.left.right.right.right = newNode(10)




    excludeLeftMost(root)



 


# This code is contributed by


# sanjeev2552


















                        






                        























                                    



                                    




                                    




                                    


                                



















// C# implementation of the above approach 



using System; 




using System.Collections.Generic; 



 



class GFG



{



     


// Structure of the tree node 



public class Node 



{ 



    public int data; 




    public Node left, right; 



}; 


 


// Utility method to create a node 



static Node newNode(int data) 



{ 



    Node node = new Node(); 




    node.data = data; 




    node.left = node.right = null; 




    return (node); 



} 


 


// Function to print all the nodes 


// except the leftmost in every level 


// of the given binary tree 


// with level order traversal 



static void excludeLeftmost(Node root) 



{ 



    // Base Case 




    if (root == null) 




        return; 



 



    // Create an empty queue for level 




    // order traversal 




    Queue<Node> q = new Queue<Node>(); 



 



    // Enqueue root 




    q.Enqueue(root); 



 



    while (true) 




    { 



 



        // nodeCount (queue size) indicates 




        // number of nodes at current level. 




        int nodeCount = q.Count; 




        if (nodeCount == 0) 




            break; 



 



        // Initialize leftmost as true 




        // just before the beginning 




        // of each level 




        Boolean leftmost = true; 



 



        // Dequeue all nodes of current level 




        // and Enqueue all nodes of next level 




        while (nodeCount > 0)




        { 




            Node node = q.Peek(); 



 



            // Switch leftmost flag after processing 




            // the leftmost node 




            if (leftmost) 




                leftmost = !leftmost; 



 



            // Print all the nodes except leftmost 




            else




                Console.Write( node.data + " "); 




            q.Dequeue(); 




            if (node.left != null) 




                q.Enqueue(node.left); 




            if (node.right != null) 




                q.Enqueue(node.right); 




            nodeCount--; 




        } 




        Console.WriteLine(); 




    } 



} 


 


// Driver code 



public static void Main(String []args)



{ 



    Node root = newNode(1); 




    root.left = newNode(2); 




    root.right = newNode(3); 




    root.left.left = newNode(4); 




    root.left.right = newNode(5); 




    root.right.left = newNode(6); 




    root.right.right = newNode(7); 




    root.left.right.left = newNode(8); 




    root.left.right.right = newNode(9); 




    root.left.right.right.right = newNode(10); 



 



    excludeLeftmost(root); 



}


}


 


// This code is contributed by PrinciRaj1992 


















                        






                        























                                    



                                    




                                    




                                    


                                



















<script>


 


// Javascript implementation of the approach


 


// Structure of the tree node 


class Node


{



    constructor(data)




    {




        this.left = null;




        this.right = null;




        this.data = data;




    }



}


 


// Utility method to create a node 



function newNode(data) 



{ 



    let node = new Node(data); 




    return (node); 



} 


 


// Function to print all the nodes 


// except the leftmost in every level 


// of the given binary tree 


// with level order traversal 



function excludeLeftmost(root) 



{ 



     



    // Base Case 




    if (root == null) 




        return; 



 



    // Create an empty queue for level 




    // order traversal 




    let q = []; 



 



    // Enqueue root 




    q.push(root); 



 



    while (true) 




    { 




         



        // nodeCount (queue size) indicates 




        // number of nodes at current level. 




        let nodeCount = q.length; 




        if (nodeCount == 0) 




            break; 



 



        // Initialize leftmost as true 




        // just before the beginning 




        // of each level 




        let leftmost = true; 



 



        // Dequeue all nodes of current level 




        // and Enqueue all nodes of next level 




        while (nodeCount > 0)




        { 




            let node = q[0]; 



 



            // Switch leftmost flag after processing 




            // the leftmost node 




            if (leftmost) 




                leftmost = !leftmost; 



 



            // Print all the nodes except leftmost 




            else




                document.write(node.data + " "); 




                 



            q.shift(); 




            if (node.left != null) 




                q.push(node.left); 




            if (node.right != null) 




                q.push(node.right); 




                 



            nodeCount--; 




        } 




        document.write("</br>"); 




    } 



} 


 


// Driver code


let root = newNode(1); 


root.left = newNode(2); 


root.right = newNode(3); 


root.left.left = newNode(4); 


root.left.right = newNode(5); 


root.right.left = newNode(6); 


root.right.right = newNode(7); 


root.left.right.left = newNode(8); 


root.left.right.right = newNode(9); 


root.left.right.right.right = newNode(10); 


 


excludeLeftmost(root); 


 


// This code is contributed by divyeshrabadiya07


 


</script>


















                        






                        








Output: 

3 
5 6 7 
9


 



	

        Article Tags : 
        

            DSA
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