Leetcode - 226. Invert Binary Tree

One of the most elegant problems in tree manipulation is inverting a binary tree — essentially flipping it along its vertical axis. It's a simple yet beautiful example of recursion and tree traversal. Let’s dive into how we can solve this in JavaScript, and explore alternate approaches and their complexities. ✅ Recursive Solution (Elegant and Classic) /** * Definition for a binary tree node. * function TreeNode(val, left, right) { * this.val = (val===undefined ? 0 : val) * this.left = (left===undefined ? null : left) * this.right = (right===undefined ? null : right) * } */ /** * @param {TreeNode} root * @return {TreeNode} */ var invertTree = function(root) { if (root === null) return null; // Recursively invert subtrees first const left = invertTree(root.left); const right = invertTree(root.right); // Swap using array destructuring (clean and readable) [root.left, root.right] = [right, left]; return root; };

Apr 19, 2025 - 20:37

One of the most elegant problems in tree manipulation is inverting a binary tree — essentially flipping it along its vertical axis. It's a simple yet beautiful example of recursion and tree traversal.

Let’s dive into how we can solve this in JavaScript, and explore alternate approaches and their complexities.

✅ Recursive Solution (Elegant and Classic)

/**
 * Definition for a binary tree node.
 * function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */

/**
 * @param {TreeNode} root
 * @return {TreeNode}
 */
var invertTree = function(root) {
    if (root === null) return null;

    // Recursively invert subtrees first
    const left = invertTree(root.left);
    const right = invertTree(root.right);

    // Swap using array destructuring (clean and readable)
    [root.left, root.right] = [right, left];

    return root;
};