OpenAI launched GPT-5.5 Instant

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This week, we’ll cover the most popular Binary Tree problem. Are you ready for it?

Today we will cover:

• Invert Binary Tree

• How text search works

Read time: under 4 minutes

CODING CHALLENGE

Invert Binary Tree

Given the root of a binary tree, invert the tree, and return its root.

Example 1:

Input: root = [4,2,7,1,3,6,9]
Output: [4,7,2,9,6,3,1]

Solve the problem here before reading the solution.

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SOLUTION

To invert a binary tree, we need to swap the left and right children of every node in the tree. We can use a recursive approach to solve this problem.

For each node, we'll first recursively invert its left and right subtrees. Then, we'll swap its left and right children. The base case is when we reach a null node.

The time complexity of this solution is O(n), where n is the number of nodes in the tree.

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SYSTEM DESIGN

How text search works?

When you have a large database table with millions of records, searching through it can be painfully slow. Think about a table with customer information containing names, addresses, phone numbers, and other details.

Let’s say you want to find all customers whose name contains "Smith". Without a search index, the database has to check every single row in the table one by one. This is called a full table scan, and it's highly inefficient.

A search index solves this performance problem. It's a specialized data structure that stores your data in a way that makes searching much faster. When you search for "Smith" in a database with a proper search index, instead of checking every row, the database uses the index to jump directly to the relevant records.

This is possible because database contains a mapping between a word or token and the records that contain that token. This is similar to how any database index works. But search indexes are specifically designed to handle text searches efficiently. They can quickly find partial matches, handle different word forms, and even account for common misspellings.

Apache Lucene is one of the most popular open-source search index implementations. Lucene handles all the complex work of creating and maintaining search indexes like including breaking text into searchable terms, removing common words, and storing the processed data efficiently.

Elasticsearch, built on top of Lucene, takes these capabilities even further. It's a distributed search engine that can handle massive amounts of data across multiple servers. Many major websites and applications use Elasticsearch to power their search features. It provides a simple way to set up search functionality that can scale as your data grows, and it includes features like real-time search, automatic suggestions, and analytics capabilities.

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NEWS

This Week in the Tech World

OpenAI rolls out GPT-5.5 Instant: OpenAI made GPT-5.5 Instant the new default model for ChatGPT, focused on cutting hallucinations in law, medicine, and finance while keeping latency low. Developers gain API access via "chat-latest".

Musk admits xAI distilled OpenAI models: In court, Elon Musk acknowledged xAI had, to some extent, distilled OpenAI models. Distillation uses outputs from a stronger model to train another, a common but increasingly controversial practice in AI.

AWS lets AI agents run virtual desktops: Amazon Web Services launched a preview that lets AI agents access and operate WorkSpaces virtual desktops with assigned identities, making it easier to track agent behavior and separate human from machine actions.

OpenAI hands Codex to 8,000 developers: OpenAI turned its sold-out GPT-5.5 event into a month-long Codex giveaway for 8,000 developers. The move puts its coding tools in more hands as competition in AI-assisted software development intensifies.

Anthropic launches AI agents for finance: Anthropic rolled out 10 AI agents built for banks, insurers, asset managers, and fintechs. The tools handle pitchbook drafting, financial statement review, credit memo prep, and compliance escalation.

U.S. to vet frontier AI models pre-release: Google DeepMind, Microsoft, and xAI agreed to let the U.S. Commerce Department's AI safety unit review new models before public release. Reviews will focus on capabilities and national security risks.

Samsung crosses $1T market cap: Samsung hit a $1 trillion valuation, becoming the second Asian company after TSMC to do so. Shares surged over 15% in a single day, fueled by investor confidence in its AI memory and semiconductor businesses.

China eyes DeepSeek at $50B valuation: China is reportedly preparing to invest in DeepSeek at around a $50 billion valuation. The move comes as Beijing pushes to strengthen domestic AI champions amid U.S. chip restrictions and global competition.

BONUS

Just for laughs 😏

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