Find sum of nodes in binary tree ( java/ non-recursive/ example)

• Given a binary tree, calculate sum of all nodes of a binary tree.
• Traverse the binary tree using level order traversal or breadth first search (bfs) algorithm.
• Accumulate sum at each level of a binary tree & we will get sum of all nodes.

Example: find sum of all nodes in a binary tree using java

The Level order traversal of binary tree shown in Fig 1 is as follows:

• Visit the Level 0 and find out sum at nodes at level o,
  • Total Sum = 55 & Go to next level
• Visit the Level 1 and Sum at Level 1 = 90 (50 + 40).
  • Total Sum = 55 + 90 =   145 & Go to next level
• Visit the Level 2 & Sum at Level 2 = 240 (25+80+45+90)
• Total Sum = 145 + 240 = 385. (Refer Fig 2)

Time complexity of algorithm is O(n).

Program: calculate sum of nodes in java using non recursive algorithm

1.) SumOfNodes Class:

• SumOfNodes class is responsible for calculating sum of all nodes in a binary tree using BFS algorithm.

package org.learn.Question;

import java.util.LinkedList;
import java.util.Queue;

public class SumOfNodes {

	public static int sumOfNodes(Node root) {
		if (root == null) {
			System.out.println("Tree is empty");
			return -1;
		}
		Queue<Node> queue = new LinkedList<Node>();
		queue.offer(root);
		int totalSum = 0;
		while (!queue.isEmpty()) {
			Node node = queue.poll();
			totalSum += node.data;
			if (node.left != null) {
				queue.offer(node.left);
			}
			if (node.right != null) {
				queue.offer(node.right);
			}
		}
		return totalSum;
	}
}

2.) Node Class:

• Node class is representing the nodes of a binary tree.

package org.learn.Question;

public class Node {
	public int data;
	public Node left;
	public Node right;

	public Node(int num) {
		this.data = num;
		this.left = null;
		this.right = null;
	}

	public Node() {
		this.left = null;
		this.right = null;
	}

	public static Node createNode(int number) {
		return new Node(number);
	}
}

3.) App Class:

• We are creating the binary tree in main method.
• We are calling method of SumOfNodes class, to calculate the sum of all nodes using BFS algorithm.

package org.learn.Client;

import org.learn.Question.Node;
import org.learn.Question.SumOfNodes;

public class App {
	public static void main(String[] args) {
		// root level 0
		Node A = Node.createNode(55);
		// Level 1
		Node B = Node.createNode(50);
		Node C = Node.createNode(40);
		// Level 2
		Node D = Node.createNode(25);
		Node E = Node.createNode(80);
		Node F = Node.createNode(45);
		Node G = Node.createNode(90);

		// connect Level 0 and 1
		A.left = B;
		A.right = C;
		// connect level 1 and level 2
		B.left = D;
		B.right = E;
		C.left = F;
		C.right = G;
		int totalSum = SumOfNodes.sumOfNodes(A);
		System.out.println("Sum of nodes in a binary tree : " + totalSum);
	}
}

Output: find sum of nodes in java using recursive algorithm

Sum of nodes in a binary tree : 385

     Download code – sum nodes binary tree (BFS)