Program to Calculate the Difference Between the Sum of the Odd Level and Even Level Nodes of a Binary Tree

Q. Program to calculate the difference between the sum of the odd level and even level nodes of a Binary Tree.

Explanation

In this program, we need to calculate the difference between the sum of nodes present at odd levels and sum of nodes present at even levels. Suppose, if a tree contains 5 levels, then

Program to calculate the difference between the sum of the odd level and even level nodes of a Binary Tree

In the above diagram, odd levels are represented using blue dotted lines and even with green.

OddLevelSum = 1 + 4 + 5 + 6 = 16
EvenLevelSum = 2 + 3 = 5
Difference = |16 - 5| = 11

Algorithm

Define Node class which has three attributes namely: data, left, and right. Here, left represents the left child of the node and right represents the right child of the node.
When a node is created, Assign the data part of a node with an appropriate value having its left and right child as NULL.
Define another class which has an attribute root.
1. Root represents the root node of the tree having null value initially.
The difference() will calculate the difference between the sum of nodes at the odd and even levels:
1. Traverse through the binary tree level wise using Queues.
2. Keep track of current level using the variable currentLevel.
3. If the currentLevel is divisible by 2, then add all the values of nodes present in currentLevel to variable evenLevel. Else, add all the values of nodes to variable oddLevel.
4. Calculate the difference by subtracting value present in evenLevel from oddLevel.

Solution

Python

#Represent a node of binary tree
class Node:
    def __init__(self,data):
        #Assign data to the new node, set left and right children to None
        self.data = data;
        self.left = None;
        self.right = None;
 
class DiffOddEven:
    def __init__(self):
        #Represent the root of binary tree
        self.root = None;
        
    #difference() will calculate the difference between sum of odd and even levels of binary tree
    def difference(self):
        oddLevel = 0;
        evenLevel = 0;
        diffOddEven = 0;
        
        #Variable nodesInLevel keep tracks of number of nodes in each level
        nodesInLevel = 0;
        
        #Variable currentLevel keep track of level in binary tree
        currentLevel = 0;
        
        #queue will be used to keep track of nodes of tree level-wise
        queue = [];
        
        #Check if root is None
        if(self.root == None):
            print("Tree is empty");
            return 0;
        else:
            #Add root node to queue as it represents the first level
            queue.append(self.root);
            currentLevel = currentLevel + 1;
            
            while(len(queue) != 0):
                #Variable nodesInLevel will hold the size of queue i.e. number of elements in queue
                nodesInLevel = len(queue);
                
                while(nodesInLevel > 0):
                    current = queue.pop(0);
                    
                    #Checks if currentLevel is even or not.
                    if(currentLevel % 2 == 0):
                        #If level is even, add nodes's to variable evenLevel
                        evenLevel = evenLevel + current.data;
                    else:
                        #If level is odd, add nodes's to variable oddLevel
                        oddLevel = oddLevel + current.data;
                        
                    #Adds left child to queue
                    if(current.left != None):
                        queue.append(current.left);
                    #Adds right child to queue
                    if(current.right != None):
                        queue.append(current.right);
                    nodesInLevel = nodesInLevel - 1;
                currentLevel = currentLevel + 1;
            #Calculates difference between oddLevel and evenLevel
            diffOddEven = abs(oddLevel - evenLevel);
        return diffOddEven;    
        
bt = DiffOddEven();
#Add nodes to the binary tree
bt.root = Node(1);
bt.root.left = Node(2);
bt.root.right = Node(3);
bt.root.left.left = Node(4);
bt.root.right.left = Node(5);
bt.root.right.right = Node(6);
 
#Display the difference between sum of odd level and even level nodes
print("Difference between sum of odd level and even level nodes: " + str(bt.difference()));

Output:

Difference between sum of odd level and even level nodes: 11

C

#include <stdio.h>
#include <stdlib.h>
 
//Represent a node of binary tree
struct node{
    int data;
    struct node *left;
    struct node *right;
};
 
//Represent the root of binary tree
struct node *root = NULL;
 
//createNode() will create a new node
struct node* createNode(int data){
    //Create a new node
    struct node *newNode = (struct node*)malloc(sizeof(struct node));
    //Assign data to newNode, set left and right child to NULL
    newNode->data = data;
    newNode->left = NULL;
    newNode->right = NULL;
    
    return newNode;
}
 
//Queue will be used to keep track of nodes of tree level-wise
struct node *queue[100];
int rear = 0, front = -1, size = 0;
 
//Adds a node to queue
void enqueue(struct node *temp){
    queue[rear++] = temp;
    size++;
}
 
//Deletes a node from queue
struct node *dequeue(){
    size--;
    return queue[++front];
}
 
//difference() will calculate the difference between sum of odd and even levels of binary tree
int difference() {
    int oddLevel = 0, evenLevel = 0, diffOddEven = 0;
      
    //Variable nodesInLevel keep tracks of number of nodes in each level
    int nodesInLevel = 0;
    
    //Variable currentLevel keep track of level in binary tree
    int currentLevel = 0;
    
    //Check if root is null
    if(root == NULL) {
        printf("Tree is empty\n");
        return 0;
    }
    else {
        //Add root node to queue as it represents the first level
        enqueue(root);
        currentLevel++;
        
        while(size != 0) {
              
            //Variable nodesInLevel will hold the size of queue i.e. number of elements in queue
            nodesInLevel = size;
            
            while(nodesInLevel > 0) {
                  struct node *current = dequeue();
                  
                //Checks if currentLevel is even or not.
                if(currentLevel % 2 == 0)
                    //If level is even, add nodes's to variable evenLevel
                    evenLevel += current->data;
                else
                    //If level is odd, add nodes's to variable oddLevel
                    oddLevel += current->data;
                  
                //Adds left child to queue
                if(current->left != NULL)
                    enqueue(current->left);
                //Adds right child to queue
                if(current->right != NULL) 
                    enqueue(current->right);
                nodesInLevel--;
            }
            currentLevel++;
        }
        //Calculates difference between oddLevel and evenLevel
        diffOddEven = abs(oddLevel - evenLevel);
    }
    return diffOddEven;
  }
    
int main(){
    
    //Add nodes to the binary tree
    root = createNode(1);
    root->left = createNode(2);
    root->right = createNode(3);
    root->left->left = createNode(4);
    root->right->left = createNode(5);
    root->right->right = createNode(6);
    
    //Display the difference between sum of odd level and even level nodes
    printf("Difference between sum of odd level and even level nodes: %d", difference());
    
    return 0;
}

Output:

Difference between sum of odd level and even level nodes: 11

JAVA

import java.util.LinkedList;
import java.util.Queue;
 
public class DiffOddEven {
    
    //Represent a node of binary tree
    public static class Node{
        int data;
        Node left;
        Node right;
        
        public Node(int data){
            //Assign data to the new node, set left and right children to null
            this.data = data;
            this.left = null;
            this.right = null;
            }
        }
    
    //Represent the root of binary tree
    public Node root;
  
    public DiffOddEven(){
        root = null;
    }
 
    //difference() will calculate the difference between sum of odd and even levels of binary tree
    public int difference() {
          int oddLevel = 0, evenLevel = 0, diffOddEven = 0;
          
          //Variable nodesInLevel keep tracks of number of nodes in each level
          int nodesInLevel = 0;
          
          //Variable currentLevel keep track of level in binary tree
          int currentLevel = 0;
          
          //Queue will be used to keep track of nodes of tree level-wise
          Queue<Node> queue = new LinkedList<Node>();
          
          //Check if root is null
          if(root == null) {
              System.out.println("Tree is empty");
              return 0;
          }
          else {
              //Add root node to queue as it represents the first level
              queue.add(root);
              currentLevel++;
              
              while(queue.size() != 0) {
                  
                  //Variable nodesInLevel will hold the size of queue i.e. number of elements in queue
                  nodesInLevel = queue.size();
                  
                  while(nodesInLevel > 0) {
                      Node current = queue.remove();
                      
                    //Checks if currentLevel is even or not.
                      if(currentLevel % 2 == 0)
                          //If level is even, add nodes's to variable evenLevel
                          evenLevel += current.data;
                      else
                          //If level is odd, add nodes's to variable oddLevel
                          oddLevel += current.data;
                      
                      //Adds left child to queue
                      if(current.left != null)
                          queue.add(current.left);
                      //Adds right child to queue
                      if(current.right != null) 
                          queue.add(current.right);
                     nodesInLevel--;
                  }
                  currentLevel++;
              }
              //Calculates difference between oddLevel and evenLevel
              diffOddEven = Math.abs(oddLevel - evenLevel);
          }
          return diffOddEven;
      }
  
    public static void main (String[] args) {
        
        DiffOddEven bt = new DiffOddEven();
        //Add nodes to the binary tree
        bt.root = new Node(1);
        bt.root.left = new Node(2);
        bt.root.right = new Node(3);
        bt.root.left.left = new Node(4);
        bt.root.right.left = new Node(5);
        bt.root.right.right = new Node(6);
    
        //Display the difference between sum of odd level and even level nodes
        System.out.println("Difference between sum of odd level and even level nodes: " + bt.difference());
}
}

Output:

Difference between sum of odd level and even level nodes: 11

C#

using System;
using System.Collections.Generic;
namespace Tree 
{                     
    public class Program
    {
        //Represent a node of binary tree
        public class Node<T>{
            public T data;
            public Node<T> left;
            public Node<T> right;
            
            public Node(T data) {
                //Assign data to the new node, set left and right children to null
                this.data = data;
                this.left = null;
                this.right = null;
            }
        }
        
        public class DiffOddEven<T>{
            //Represent the root of binary tree
            public Node<T> root;
            
            T[] treeArray;
            int index = 0;
            
            public DiffOddEven(){
                root = null;
            }
            
            //difference() will calculate the difference between sum of odd and even levels of binary tree
            public int difference() {
                int oddLevel = 0, evenLevel = 0, diffOddEven = 0;
                  
                //Variable nodesInLevel keep tracks of number of nodes in each level
                int nodesInLevel = 0;
                
                //Variable currentLevel keep track of level in binary tree
                int currentLevel = 0;
                
                //Queue will be used to keep track of nodes of tree level-wise
                Queue<Node<T>> queue = new Queue<Node<T>>();
                
                //Check if root is null
                if(root == null) {
                    Console.WriteLine("Tree is empty");
                      return 0;
                }
                else {
                    //Add root node to queue as it represents the first level
                    queue.Enqueue(root);
                    currentLevel++;
                    
                    while(queue.Count != 0) {
                      
                        //Variable nodesInLevel will hold the size of queue i.e. number of elements in queue
                        nodesInLevel = queue.Count;
                        
                        while(nodesInLevel > 0) {
                            Node<T> current = queue.Dequeue();
                          
                            //Checks if currentLevel is even or not.
                            if(currentLevel % 2 == 0)
                                //If level is even, add nodes's to variable evenLevel
                                evenLevel += Convert.ToInt32(current.data);
                              else
                                //If level is odd, add nodes's to variable oddLevel
                                oddLevel += Convert.ToInt32(current.data);
                          
                            //Adds left child to queue
                            if(current.left != null)
                                queue.Enqueue(current.left);
                            //Adds right child to queue
                            if(current.right != null) 
                                queue.Enqueue(current.right);
                             nodesInLevel--;
                        }
                        currentLevel++;
                    }
                    //Calculates difference between oddLevel and evenLevel
                    diffOddEven = Math.Abs(oddLevel - evenLevel);
                }
                return diffOddEven;
            }    
        }
        
        public static void Main()
        {
            DiffOddEven<int> bt = new DiffOddEven<int>();
            //Add nodes to the binary tree
            bt.root = new Node<int>(1);
            bt.root.left = new Node<int>(2);
            bt.root.right = new Node<int>(3);
            bt.root.left.left = new Node<int>(4);
            bt.root.right.left = new Node<int>(5);
            bt.root.right.right = new Node<int>(6);
            
            //Display the difference between sum of odd level and even level nodes
            Console.WriteLine("Difference between sum of odd level and even level nodes: " + bt.difference());                
        }    
    }
}

Output:

Difference between sum of odd level and even level nodes: 11

PHP

<!DOCTYPE html>
<html>
<body>
<?php
//Represent a node of binary tree
class Node{
    public $data;
    public $left;
    public $right;
    
    function __construct($data){
        //Assign data to the new node, set left and right children to NULL
        $this->data = $data;
        $this->left = NULL;
        $this->right = NULL;
    }
}
    
class DiffOddEven{
    //Represent the root of binary tree
    public $root;
    function __construct(){
        $this->root = NULL;
    }
    
    //difference() will calculate the difference between sum of odd and even levels of binary tree
    function difference(){
        $oddLevel = 0;
        $evenLevel = 0;
        $diffOddEven = 0;
        
        //Variable nodesInLevel keep tracks of number of nodes in each level
        $nodesInLevel = 0;
          
        //Variable currentLevel keep track of level in binary tree
        $currentLevel = 0;
        
        //queue will be used to keep track of nodes of tree level-wise
        $queue = array();
        
        //Check if root is null
        if($this->root == NULL) {
            print("Tree is empty <br>");
            return 0;
        }
        else {
            //Add root node to queue as it represents the first level
            array_push($queue,$this->root);
            $currentLevel++;
            
            while(sizeof($queue) != 0) {
                
                //Variable nodesInLevel will hold the size of queue i.e. number of elements in queue
                $nodesInLevel = sizeof($queue);
                while($nodesInLevel > 0) {
                    $current = array_shift($queue);
                    
                    //Checks if currentLevel is even or not.
                    if($currentLevel % 2 == 0)
                        //If level is even, add nodes's to variable evenLevel
                          $evenLevel += $current->data;
                    else
                        //If level is odd, add nodes's to variable oddLevel
                        $oddLevel += $current->data;
                  
                    //Adds left child to queue
                    if($current->left != NULL)
                        array_push($queue, $current->left);
                    //Adds right child to queue
                    if($current->right != NULL) 
                        array_push($queue, $current->right);
                    $nodesInLevel--;
              }
              $currentLevel++;
          }
          //Calculates difference between oddLevel and evenLevel
          $diffOddEven = abs($oddLevel - $evenLevel);
        }
        return $diffOddEven;
    }    
}    
 
$bt = new DiffOddEven();
//Add nodes to the binary tree
$bt->root = new Node(1);
$bt->root->left = new Node(2);
$bt->root->right = new Node(3);
$bt->root->left->left = new Node(4);
$bt->root->right->left = new Node(5);
$bt->root->right->right = new Node(6);
 
//Display the difference between sum of odd level and even level nodes
print "Difference between sum of odd level and even level nodes: " . $bt->difference();
?>
</body>
</html>

Output:

Difference between sum of odd level and even level nodes: 11

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