Find level in binary tree having maximum sum (java/ non-recursive/ example)

• Given a binary tree, find out the level, which is having maximum sum using non recursive algorithm.
  • Traverse the binary tree using level order traversal or breadth first search (BFS) algorithm.
• Root node of binary tree is at level 0.
  • We can find out the level of rest of nodes wrt. root node.
• We have discussed the similar problem, find out the height of binary tree using level order traversal.

Example: Find level having maximum sum in a binary tree (java)

Find out the level, which having maximum sum, for a given binary tree shown in Fig 2. Let us calculate the sum at each level.

In a given binary tree, Level 2 has maximum sum of 240.

Algorithm: find level having max sum in a binary tree (iterative method)

• Root is at level 0, push root node to queue.
• Create variable to store maxSum & level.
• Push null as level delimiter, to the queue.
• Iterate through the Queue
  • Calculate the local sum
  • Pop node from queue
  • If popped up node is null,
    •  We are at next level.
      • Update maxSum if it is less than local sum.
        • Save the level of local sum.
• Add next level children (left or/and right nodes)
• Once we exit the loop, we will get the maximum sum and level.

Time complexity of algorithm is O(n).

Program: find out level having max sum in java (breadth first search algo.)

1.) MaxSumLevel Class:

• MaxSumLevel class is responsible for finding the level, which is having maximum sum.
• Traverse the binary tree using level order traversal or breadth first search algorithm.

package org.learn.Question;

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

public class MaxSumLevel {
 public static void maxSumLevel(Node root) {
  if (root == null) {
   System.out.println("Tree is empty");
   return;
  }
  Queue<Node> queue = new LinkedList<Node>();
  queue.offer(root);
  // level delimiter
  queue.offer(null);

  int maxSum = 0;
  int level = 0;
  // default root level
  int localLevel = 0;
  int localSum = 0;
  while (!queue.isEmpty()) {
   Node node = queue.poll();
   // Level change
   if (null == node) {
    if (!queue.isEmpty()) {
     // level delimiter
     queue.offer(null);
    }

    if (localSum > maxSum) {
     maxSum = localSum;
     level = localLevel;
    }
    // Reset the level sum for next level calculation
    localSum = 0;
    localLevel++;
   } else {
    if (node.left != null) {
     queue.offer(node.left);
    }
    if (node.right != null) {
     queue.offer(node.right);
    }
    localSum += node.data;
   }
  }
  System.out.println("Max Sum = " + maxSum + " is at Level = " + level);
 }
}

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 calling the method of MaxSumLevel class, to find the level, which is having maximum sum.

package org.learn.Client;

import org.learn.Question.MaxSumLevel;
import org.learn.Question.Node;

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);
  // Level 3
  Node H = Node.createNode(10);
  Node I = Node.createNode(35);
  Node J = Node.createNode(65);
  Node K = Node.createNode(75);

  // 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;
  // connect level 2 and level 3
  F.left = H;
  F.right = I;
  G.left = J;
  G.right = K;
  MaxSumLevel.maxSumLevel(A);
 }
}

Output: level in a binary having maximum sum using java

Max Sum = 240 is at Level = 2

Download code – find level in binary tree maximum sum in java