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> |
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