Hi Everyone!

Hope you’re all having a great day!

Here’s your Interview Problem, Yesterday’s Solution and Tech Snippets for the day!

Tech Dive

Our last tech dives were on Distributed Systems and Database Sharding!

• Distributed Systems Tech Dive

• Database Sharding Tech Dive

Tech Snippets

• The Rise of the Time Series Database

  • One of the most notable trends in databases is the Time Series database. Last year, TSDB was the fastest growing type of database in the enterprise space.

  • Time series data is a sequence of data points collected over time (denoted by timestamps). Time series databases (TSDB) are optimized for storing and serving time series data very quickly.

  • TSDB can offer quick answers to statistical questions about data for a range of time periods. They also make maintenance chores (like clearing out old data) extremely easy to automate

  • Time series data is becoming more critical for enterprises with things like log files, IoT data, event tracking, etc. Many of these data files can be indexed by time.

  • Popular Time Series Databases include…

    • InfluxDB

    • Prometheus

    • Druid

    • Timescale DB

• Apple plans to launch a Podcast subscription service

  • Apple has been shifting their business strategy focus on subscription products with Apple Music, Apple TV+ and Apple Fitness+.

  • Apple is now looking at the Podcasting market as an area for a new subscription product.

  • Apple is considering allowing podcasters to charge for episode access on the Podcasts app. This could entice creators to commit exclusively to Apple Podcasts.

  • Apple Podcasts is currently the dominant podcast player with Spotify being a #2.

  • Spotify shares tumbled 7% after the news came out as Apple’s increased focus on podcasting could be a threat to Spotify

Interview Question

Given an array nums of n integers and an integer target, find three integers in nums such that the sum is closest to target.

Return the sum of the three integers.

You may assume that each input would have exactly one solution.

Here’s the question in LeetCode.

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Previous Solution

As a refresher, here’s the previous question

You are given a binary tree containing digits from 0 - 9 only.

Each root to leaf path represents a number. A root to leaf path of 1 -> 3 -> 4 represents the number 134.

Find the total sum of all root to leaf numbers.

Here’s the question in LeetCode.

Solution

We can solve this question with a tree traversal in a Depth First fashion.

We’ll keep track of the current path by using an integer.

Everytime we want to add a digit to the integer, we multiply it by 10 and then take the sum with the new digit.

Everytime we want to remove the last digit, we divide the number by 10 and truncate it.

We’ll keep track of the sum of all the paths with a variable called totalSum.

We use a recursive function to do our Depth First traversal.

In our recursive function, we first add the digit at the current node to a variable that keeps track of the path (curVal). We multiply curVal by 10 and then add the sum with the new digit at the current node.

If the current node is a leaf, then we add curVal to totalSum

Otherwise, we recurse on the node’s children.

After, we remove the digit we added to curVal (similar to how you’d do in backtracking) by dividing curVal by 10 and truncating.

After the traversal, we can return totalSum.

Here’s the solution in Python 3

Best,

Arpan