Explore

EXPLORE THE CATALOGSupercharge your career with 700+ hands-on courses

View All Courses

Python

Java

JavaScript

React

Docker

Vue JS

Web Dev

DevOps

AWS

LEARNING TOOLSExplore the industry's most complete learning platform

CoursesLevel up your skills

Cloud LabsSetup-free practice with Cloud Services

Skill PathsAchieve learning goals

ProjectsBuild real-world applications

Mock InterviewsNewAI-Powered interviews

Personalized Interview PrepNewGet a custom roadmap tailored to your goals

AssessmentsBenchmark your skills

Personalized PathsGet the right resources for your goals

LEARN TO CODE

Check out our beginner friendly courses.

Pricing

For Business

Resources

NewsletterCurated insights on AI, Cloud & System Design

BlogFor developers, By developers

Free CheatsheetsDownload handy guides for tech topics

Learn Ruby from Scratch/

...

Exercise 3: Sum the Rows of a Matrix

Write code that calculates the array produced by summing the entries of each row of a matrix.

We'll cover the following...

Problem statement
- Example
- Try it yourself

Press + to interact

The Big Picture

Variables

Built-in Class: Numeric

Built-in Class: String

Built-in Classes: TrueClass, FalseClass, and NilClass

Built-in Class: Symbol

Built-in Class: Array

Built-in Class: Hash

Objects

Methods

Operators are Methods

Blocks

Get Ready for Some More Drill!

Conditionals

Coding Challenge: Truthiness and Equivalence

Lets Run Another Lap with Hashes

Writing Classes

The Mailbox Project

Spotlight on Things Unremarked

Advanced Topics

Your Toolkit

Appendix: Mailbox Project Prerequisite

Exercise 3: Sum the Rows of a Matrix