☕ Your groceries can fly?

Hey Guys,

Hope you’re all having an amazing day! Here’s your Interview Problem and Industry News for the day!

Interview Problem

Let’s say you have a photo sharing app that is used by every person on Earth. How would you estimate the hardware cost of the servers necessary to run the app?

Your thought process matters more than the exact numbers.

We’ll send you our solution tomorrow!

Industry News

• Truepill raises $75 million to expand it’s Telehealth and Pill Delivery Platform - Truepill (YC S17) is a healthcare services startup that provides pharmacy fulfillment services (B2B - so they deliver medications to pharmacies like CVS or Walgreens) and telehealth (they connect a network of thousands of doctors with patients). The company is known as the “AWS for pharmacies”. They’ve now raised a round of $75 million dollars with a revenue of $200 million dollars. The money will be used to grow existing businesses but also expand into lab testing. This lab testing, that used to be confined to a doctor’s office, will now be offered to patients remotely.

• Apple vs. Epic - The fight between Apple and Epic Games has gone to new highs. For context, Epic Games is the company behind Unreal Engine, which they’ve used to develop popular games like Fortnite, Gears of War and Infinity Blade. Apple has been feuding with Epic over the Apple App Store’s “30% cut”, where the App Store gets 30% of an App’s revenue from in-game content. Apple has now filed counterclaims against Epic… seeking damages for breach of contract. Epic has begun to warn Fortnite users that Apple will no longer allow them to sign into the app with “Sign In With Apple”, and that Fortnite users may be prevented from accessing their data on the app due to that.

• Walmart is testing drone delivery for groceries and household items - The world’s largest retailer has started to test drone delivery of grocery and household items from its stores in Fayetteville, North Carolina. The drones are from Israeli startup Flytrex Aviation and they can fly more than 6 miles with carrying packages that weigh up to 6.6 lbs. The drones take off from a landing pad near the store. Walmart has also recently started a membership program, Walmart+, to compete with Amazon’s Prime service.

Previous Solution

As a reminder, here’s the previous question

Given a string, return the index of its first unique character. If a unique character does not exist, return -1

Examples

Input: “aa”

Output: -1

Input: “Interview”

Output: 1

Solution

This question can be solved by utilizing a hash table.

First, we should ask the interviewer how to handle capitalization. Let’s assume that we should ignore capitalization. I == i. Therefore, the first step is to convert the string to lowercase.

Now, we start with an empty hash table, and then we iterate through the string. There are 2 possible cases…

1. We come across a character that is NOT in the hash table - This character has appeared once so far. We add the character to the hash table, and set the value to it’s index

2. We come across a character that is in the hash table - This character appears multiple times in the string. We set the value of the character to None

After we iterate through the string, all the characters with a valid index as it’s value appear only once. All the characters that have None as their value appear multiple times.

We return the minimum valid index. If there isn’t one, then we return -1

Here’s a REPL with the solution in Python