Can you solve this Amazon challenge?

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Interview Master
March 27, 2024

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Welcome back, Interview Masters!

Are you ready for another coding challenge? We are going to take it easy today with a coding question frequently asked by big tech companies.

In today’s newsletter, we’ll cover:

  • Two Sum problem

  • How does Netflix work?

Read time: under 4 minutes

CODING CHALLENGE

Two Sum

Given an array of integers nums and an integer target, return indices of the two numbers such that they add up to target.

You may assume that each input would have exactly one solution, and you may not use the same element twice.

You can return the answer in any order.

Example 1:

Input: nums = [2,7,11,15], target = 9
Output: [0,1]
Explanation: Because nums[0] + nums[1] == 9, we return [0, 1].

Example 2:

Input: nums = [3,2,4], target = 6
Output: [1,2]

Example 3:

Input: nums = [3,3], target = 6
Output: [0,1]

Solve the problem here before reading the solution.

SOLUTION

To solve this problem, we'll use a hashmap (dictionary in Python) to store the indices of the elements we have seen so far. We'll iterate through the array once.

For each element, we'll calculate its complement (target - current element). We'll then check if this complement exists in our hashmap.

If it does, we've found the pair of elements that sum up to the target.

If it doesn't exist, we'll add the current element and its index to the hashmap.

This way, we can efficiently find the indices of the two numbers that add up to the target.

Time complexity of this solution is O(n) because it iterates through each element in the input list once.

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SYSTEM DESIGN EXPLAINED

How does Netflix work?

Netflix uses a custom Content Delivery Network (CDN) to stream videos efficiently. When you press play, Netflix sends a request to find the nearest CDN server with the video and then streams it to your device.

Netflix pre-stores videos on these servers to ensure smooth playback and uses a special format that adapts to your internet speed. To support different devices, Netflix converts videos into multiple formats before storing them. You can read the full article here.

NEWS

This week in the tech world

Brain Implant Plays Chess: Neuralink, Elon Musk’s company working on brain-computer interfaces, showed a video of a person successfully playing chess using a brain implant.

Reddit Debuts on Wall Street: Reddit, the popular social media platform, went public! Their IPO priced shares at $34 and soaring since, marking the first major social media debut since 2019.

Amazon Rides AI Wave: Amazon's gamble on AI pays off! Astera Labs, an AI startup they invested in, skyrocketed 72% during its IPO, reaching a market cap of nearly $9.5 billion.

Surface Gets AI Boost: Microsoft released new Surface laptops that have a special button for quickly accessing their AI assistant, Copilot. This is the first time Microsoft has added a new button to their keyboard in 30 years.

Apple's AI Event: Apple gears up for its developer conference, sparking anticipation. There are rumors about Apple finally revealing its long-awaited AI strategy.

Xiaomi's Tesla Rival: Xiaomi's CEO has announced their upcoming competitively priced electric vehicle under $69,400.

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NEXT IN CODING CHALLENGE

Best Time to Buy and Sell Stock

You are given an array prices where prices[i] is the price of a given stock on the ith day.

You want to maximize your profit by choosing a single day to buy one stock and choosing a different day in the future to sell that stock.

Return the maximum profit you can achieve from this transaction. If you cannot achieve any profit, return 0.

Join us next week to find out the solution.