Unveiling the Approach: Merging Binary Trees

Step 1: The Simple Case - Merging Root Nodes

Before diving into the complexities of merging full-fledged binary trees with all their branches and leaves, let's start simple. We'll consider the most basic case: two trees each containing only a root node.

Here's the example we'll work through:

1  1st Tree         2nd Tree         Merged Tree       
2      3               1                  4               

The Strategy for Merging Root Nodes

1. Check for Empty Trees: First, ensure that neither of the root nodes is null.
2. Sum the Values: If both roots exist, sum their values to create a new root node for the merged tree.
3. Create the Merged Root: Instantiate a new node with the sum as its value.

Code Snippet for Merging Root Nodes

Here's how you would implement these steps.

Great! We've successfully merged two single-node trees. But what happens when these trees have children?

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function Node(val) {

  this.val = val;

  this.left = this.right = null;

}

​

function mergeTrees(root1, root2) {

  // Check for empty trees

  if (!root1) return root2;

  if (!root2) return root1;

​

  // Sum the root nodes' values

  let sum = root1.val + root2.val;

​

  // Create the merged root

  let mergedRoot = new Node(sum);

​

  return mergedRoot;

}

​

// Create individual root nodes for 1st and 2nd trees

let root1 = new Node(3);

let root2 = new Node(1);

​

// Merge and get the new root

let mergedRoot = mergeTrees(root1, root2);

console.log(`Merged Root Value: ${mergedRoot.val}`);  // Output should be 4