Most asked easy problem

Welcome back!

This week’s problem has been asked by Uber, Amazon, Google and many others. And the best part - it’s an easy problem. Ready to give it a try?

Today we will cover:

• Valid Parentheses problem

• Redis vs Memcached

Read time: under 4 minutes

CODING CHALLENGE

Valid Parentheses

Given a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.

An input string is valid if:

1. Open brackets must be closed by the same type of brackets.

2. Open brackets must be closed in the correct order.

3. Every close bracket has a corresponding open bracket of the same type.

Example 1:

Input: s = "()"

Output: true

Example 2:

Input: s = "(]"

Output: false

Example 3:

Input: s = "([])"

Output: true

Solve the problem here before reading the solution.

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SOLUTION

To solve this problem, we can use a stack. We'll iterate through each character in the string. If we encounter an opening bracket, we'll push it onto the stack. If we encounter a closing bracket, we'll check if the stack is empty or if the top of the stack doesn't match the corresponding opening bracket. If either condition is true, we return false. If not, we pop the top element from the stack.

After processing all characters, we check if the stack is empty. If it is, all brackets were properly closed, and we return true. If not, there are unmatched opening brackets, so we return false.

The time complexity of this solution is O(n), where n is the length of the input string. We iterate through each character once, and stack operations (push and pop) are O(1).

SYSTEM DESIGN

Redis vs Memcached

Redis and Memcached are the two most popular tools used for caching. Both Redis and Memcached store data in memory, which makes them incredibly fast. 

Memcached is the simpler option. It's a straightforward key-value store that uses consistent hashing to distribute data across multiple nodes. This means requests for specific data always go to the same cache server, making it efficient and predictable. It supports multi-threading and uses a "least recently used" (LRU) policy to remove old data when space runs low.

Redis takes things further by offering more features. Beyond basic key-value storage, it supports complex data structures like hash maps, sorted sets, and even geo indexes - all running in memory. Redis also includes features like write-ahead logging for atomic operations and single-threaded execution for transaction support.

When should you choose one over the other? Redis is generally more developer-friendly with its built-in features and managed approach. It's great for solo developers or teams that want a powerful caching solution without much configuration. Memcached, while requiring more setup, offers more flexibility for complex caching scenarios. It's particularly useful when you need custom replication strategies or special locking mechanisms.

DEVELOPER TOOLS

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NEWS

This Week in the Tech World

Dropbox Cuts 528 Jobs: Dropbox lays off 20% of its workforce, affecting 528 employees, as CEO Drew Houston cites softening demand and organizational complexity. This follows a previous 16% cut in April 2023.

Google's AI Code Progress: Google reveals AI now writes over 25% of its code. CEO Sundar Pichai highlights AI's role in driving cloud revenue up 35% to $11.4B and improving search functionality.

Nvidia Expands in India: Nvidia partners with Reliance Industries and launches a Hindi language model. CEO Jensen Huang announces major computing infrastructure expansion, predicting India will "export AI" instead of just software.

Nadella Takes Pay Cut Over Security: Microsoft CEO Satya Nadella requested a $5.5M reduction in his cash incentive after security breaches, though his total compensation still rose 63% to $79.1M. The cut reflects his "personal accountability" for cybersecurity issues.

Oracle Launches AI Health Records: Oracle unveils new AI-powered electronic health record system, its biggest healthcare update since acquiring Cerner. The system uses voice commands and AI to help doctors spend less time on paperwork and more with patients.

Delta Sues CrowdStrike: Delta Air Lines sues CrowdStrike over a July IT outage that cost $550 million and caused 7,000 flight cancellations. CrowdStrike countersues, claiming Delta's "own negligence" caused the extended disruption.

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