BC TECH

Saved by @SteveeRogerr

Santiago
@svpino 3 years, 3 months ago 505 views

Save to PDF Share See On Twitter

11 short programming problems to stretch your imagination and make sure you are staying on your toes.

(Starting with the simple ones, they get more fun as you move towards the end.)

🧵👇

1. Write a function that reverses an array in place.

In other words, the function should not use an auxiliary array to do the work.

2. Write a function that finds the missing number in an unsorted array containing every one of the other 99 numbers ranging from 1 to 100.

3. Write a function that finds the duplicate number in an unsorted array containing every number from 1 to 100.

Only one of the numbers will appear twice.

4. Write a function that removes every duplicate value in an array.

There could be more than one value duplicated. You should remove all of them leaving a single copy of the value.

5. Write a function that finds the largest and smallest number in an unsorted array.

6. Write a function that finds a subarray whose sum is equal to a given value.

7. Write a function that finds the contiguous subarray of a given size with the largest sum.

8. Write a function that, given two arrays, finds the longest common subarray present in both of them.

9. Write a function that, given two arrays, finds the length of the shortest array that contains both input arrays as subarrays.

10. Write a function that, given an array, determines if you can partition it in two separate subarrays such that the sum of elements in both subarrays is the same.

11. Write a function that, given an array, divides it into two subarrays, such as the absolute difference between their sums is minimum.

I'd love to see some answers!

If you want more content on software engineering, machine learning, and adjacent topics, give me a follow. I post threads like this every week. You can enjoy more of this content here: @svpino.

More from Santiago

Santiago
@svpino

12 machine learning YouTube videos.

On libraries, algorithms, tools, and theory.

↓

1. Jupyter Notebooks: https://t.co/HqE9yt8TkB

2. Pandas: https://t.co/aOLh0dcGF5

3. Matplotlib: https://t.co/tKADpmihkh

4. Seaborn: https://t.co/s8EUxh6x1f

5. Numpy: https://t.co/pJoc0Lfjwm

6. Decision Trees: https://t.co/tKtUpO1K3l

7. Neural Networks: https://t.co/bc7emyjc9q

8. Scikit-Learn: https://t.co/LrKG7cMxRq

9. TensorFlow: https://t.co/fhO6T9sblU

10. PyTorch: https://t.co/5w9mJxijdd

11. Essense of Linear Algebra: https://t.co/o3kOnxl90i

12. Essense of Calculus: https://t.co/rfo7v0cpR4

Santiago
@svpino

11 key concepts of Machine Learning.

— Supervised Learning Edition —

🧵👇

😜

Before starting, remember that, if you follow me, one of your enemies will be immediately destroyed (and you'll get to read more of these threads, of course.)

And if you don't follow me, well, you just hurt my feelings.

😜

1. Labels

(Also referred to as "y")

The label is the piece of information that we are predicting.

For example:

- the animal that's shown in a picture
- the price of a house
- whether a message is spam or not

👇

2. Features

(Also referred to as "x")

These are the input variables to our problem. We use these features to predict the "label."

For example:

- pixels of a picture
- number of bedrooms of a house
- square footage of a house

👇

3. Samples

(This is also known as "examples.")

A sample is a particular instance of data (features or "x.") It could be "labeled" or "unlabeled."

👇

Advertisement

Santiago
@svpino

A topic that comes up in every interview.

Bias, variance, and their relationship with machine learning algorithms. One of the most basic concepts that you have to know by heart.

Here is a simple summary that you will easily remember.

↓

Every machine learning algorithm deals with 3 types of errors:

1. Bias error
2. Variance error
3. Irreducible error

There's nothing we can do about #3.

Let's focus on the other two.

↓ 1/5

"Bias" refers to the assumptions the model makes to simplify the process of finding answers.

The more assumptions it makes, the more biased the model is.

"Variance" refers to how much the answers given by the model will change if we use different training data.

If the answers stay the same regardless of the data, the model has low variance.

Often, linear models are high-bias, and nonlinear models are low-bias.

Example low-bias algorithms:
• Decision Trees
• SVN
• kNN

Example high-bias algorithms:
• Linear Regression
• Logistic Regression

Santiago
@svpino

Do you know what's better than a machine learning model?

Two models.

More than one model working together to solve a problem is called "an emsemble." A simple way to build this is having each model vote for an answer.

But there's a problem with this approach: ↓

I'm gonna focus here on image classification.

Let's assume you built two different models:

• Model 1: A ResNet model.
• Model 2: A one-shot model (Siamese network.)

They both solve the same problem, so you want to combine their results to pick the right answer.

The problem is that you have two models, so voting is not trivial.

What happens in this case?

• Model 1's answer: Class A
• Model 2's answer: Class B

Which one do you select?

Notice that this problem is not limited to an even number of models.

You could have 3 models, each giving you a different answer.

How do you decide which answer to choose?

There are multiple ways to approach this problem. I'll mention a few different ideas on this thread.

Important: Some of these ideas might not be feasible depending on your context. They have worked for me before on different situations, but every problem is different.

Santiago
@svpino

Some of the things I've learned in more than 20 years in the tech industry.

You need to hear these.

🧵👇

Listen to more people who don't look like you, don't speak your language, and don't come from the same place you do.

We aren't doing this near enough.

Small habits compound.

No small improvement is too small.

Just aim for something new every day, and you'll be surprised at the end.

Take responsibility.

It doesn't really matter how you feel, I'm sure you could have done better.

Always keep the big picture in mind and never lose the forest for the trees.

Be the person that pulls everyone out of the rabbit holes.

More from Tech

Novid Houellebecq (Tha...
@GarouGothic

I want to explain what happened to tumblr overnight. And why Twitter as reached it's dream (or have come ever so close to it)

Yahoo, who bought Tumblr years ago, used to have a huge adult presence on the early net. They allowed adult groups and what not.

However, people and bots (just like now) misused the service, and Yahoo were forced to make a choice. They made private the groups (and later closed them down and sold some of it to other companies) and then ended their chatrooms on yahoo messenger...

after a incident with one of the chatrooms vid cams. The damage was done, Yahoo Messenger lost a lot of people - and with the closing of the groups - backpage and Craigslist came more important.

Now backpage is no more and Craigslist is slowly passing away. Tumblr had a semi strong community, but once 2014 came around and both porn, and political bots exploded the quality started to go down,

foone
@Foone

I got a Toshiba T1200, which has a bad screen, and a dead CMOS battery, and I thought the hard drive was broken too...

but I rebooted it and heard a KTHUNK and a really loud spin-up noise and holy shit, the hard drive works!

and it still has files on it. the newest date is January 1994.

It's a 21mb hard drive, with ~37k of bad sectors.

This fucker is never going to spin up again, so I better go find some serial cables and copy shit off now.

The backlight is fucked so I'm shining a flashlight on it.
without it, it looks like this.

Advertisement

foone
@Foone

you know how Atari called the Jaguar as a "64bit system", because it had two 32bit CPUs? (or because it had a 64bit bus, but let's not worry about that)
we should apply that logic to the current generation of consoles.
So the Switch is a 256bit console. It's the Nintendo 256.

The Xbox Series X? terrible name.
Better call it the "Xbox 512 Blu-ray".
like the Jaguar CD, the Sega CD... the good old days when consoles had their media type in the name.

Boringly the PS5 is also a Playstation 512 Blu-ray, because both of them are using the same AMD Zen 2 CPU.

The Switch one is weeeird. It's built on an Nvidia Tegra X1, which is an 8 core 64-bit CPU, so that should be 512, right?

Well... no. Four of them can't be used. And later documentation doesn't even mention them.

it's some weird system where the system-on-a-chip has four Cortex-A57 cores and four Cortex-A53 cores but only the A57s are usable?

Matt Stoller
@matthewstoller

1. One of the best changes in recent years is the GOP abandoning libertarianism. Here's GOP Rep. Greg Steube: “I do think there is an appetite amongst Republicans, if the Dems wanted to try to break up Big Tech, I think there is support for that."

2. And @RepKenBuck, who offered a thoughtful Third Way report on antitrust law in 2020, weighed in quite reasonably on Biden antitrust frameworks.

3. I believe this change is sincere because it's so pervasive and beginning to result in real policy changes. Example: The North Dakota GOP is taking on Apple's app store.

Republican North Dakota legislators have introduced #SB2333, a bill that prohibits large tech companies from locking their users into a single app store or payment processor.https://t.co/PgyhgOhFAl

1/ pic.twitter.com/KZ8BMFQoPO
— Cory Doctorow #BLM (@doctorow) February 11, 2021

4. And yet there's a problem. The GOP establishment is still pro-big tech. Trump, despite some of his instincts, appointed pro-monopoly antitrust enforcers. Antitrust chief Makan Delrahim helped big tech, and the antitrust case happened bc he was recused.

5. At the other sleepy antitrust agency, the Federal Trade Commission, Trump appointed commissioners
@FTCPhillips and @CSWilsonFTC are both pro-monopoly. Both voted *against* the antitrust case on FB. That case was 3-2, with a GOP Chair and 2 Dems teaming up against 2 Rs.

Knarf
@Knarf93

@zkat__ I'm in the position that I actually find npm / yarn the best ecosystem. Whenever I use something else I always end up stubbing my toe into something thats missing / feels wrong.

Ex. Cargo seems to neither have a concept of devDependencies nor peerDependencies.

I also can't understand why it wouldn't have an "add" command to add a new dependency. And I'm no fan of Toml, json is greate (easy to parse and build tooling around), and the better option in my opinion would be json5.

C / C++ seems to just not have language package managers. The linux / bsd crowd seem to have decided that the system package manager also should be the language package manager. Which might have been fine if every Linux distro used the same system package manager.

Instead we end up with a N x M problem. Where we have a bunch of different operating systems and they all support multiple system package managers. So there's no easy way of distributing, referencing and updating C / C++ packages.

It is also my opinion that the compiler / runtime should be a package dependency. I don't like Rust's split between rustup and cargo (they should have been one tool). Similarly it would be better if you added Node as a dependency to package.json, that way we wouldn't need NVM.

You May Also Like

Vikrant
@Trading0secrets

Full technical analysis courses in one thread 🧵

For free which is Worth ₹80k 👇

⏭️How elliott wave work with examples

⏭️ Advance price action analysis

⏭️ Richard wyckoff theory

⏭️dow theory (my first video)

If you wanna learn how market behave in long term & short term

You must watch full video 🎥

Panic! in the Discord
@discord__panic

Neo-nazi group #PatriotFront held a photo op in #Chicago last weekend & is currently marching around #DC so it's as good time as any to compile a list of their identified members for folks to watch for

Who are these chuds?

Patriot Front broke away from white nationalist org Vanguard America following #unitetheright in #charlottesville after James Alex Fields was seen with a VA shield before driving his car into a crowd, murdering Heather Heyer & injuring dozens of others

Syed Robbie Javid a.k.a. Sayed Robbie Javid or Robbie Javid of Alexandria,

Happy Monday everyone :-) Let's ring in September by reacquainting ourselves with Virginia neo-Nazi and NSC Dixie affiliate Sayed "Robbie" Javid, now known by "Reform the States". Robbie is an explicitly genocidal neo-Nazi, so lets get to know him a bit better!

CW on this thread pic.twitter.com/3gzxrIo9HD
— Garfield but Anti-Fascist (@AntifaGarfield) August 31, 2020

Antoine Bernard Renard (a.k.a. “Charlemagne MD” on Discord) from Rockville, MD.

https://t.co/ykEjdZFDi6

Brandon Troy Higgs, 25, from Reisterstown,

Advertisement

$Anu Satheesh \U0001f1ee\U0001f1f3$

Anu Satheesh 🇮🇳...
@AnuSatheesh5

Samayapuram Mariamman Temple
#Trichy
#Tamilnadutemples 🚩

Samayapuram Mariamman Temple is located in Samayapuram of
Tiruchirappalli district. Mariyamman here is worshipped as Samayapurathal a form of Parashakti.
Amman vigraham here is made of sand and clay so

no abhishekam done to the main vigraham. Samayapuram Mariamman Temple is one of the famous Shakthi Sthal of Tamilnadu.

Story says that paramashiva created Kali, out of the poison that he drank during samudra mathanam. As Devi originated from the Kaalakoota/ halahala poison,

thus the name Kaali. Mariamman is believed to be a form of Kaali, and is also known as Mahamayi. It is also believed that Maharaja Dasharatha offered his prayers here.

Mariamman is Parashakti herself who blesses with prosperity and she is believed to cure all diseases.

Paramashiva, Mahavishnu and Brahma Deva are believed to have taken blessings of Mariamman here.

Om Shakti Para Shakti
🙏🕉🙏

DTBhat
@dtbhat

The thread explains my momentum scanner and how to build it in #TradePoint software.
@Definedge
Conditions :
1)EMA 8 above EMA 34 and rising
2)Candle close above previous 5 candle high
3) RSI above 60
4) Volume above previous 5 candles
5) ADX above 30
1/n

Select Double Moving Average 8 and 34
2/n

Under Patterns select Close Above Prev Bars
3/n

Qualify the candle close
4/n

RSI above 60
5/n

Sahil
@sahilypatel

A list of cool websites you might now know about

A thread 🧵

1) Learn Anything - Search tools for knowledge discovery that helps you understand any topic through the most efficient

2) Grad Speeches - Discover the best commencement speeches.

This website is made by me

3) What does the Internet Think - Find out what the internet thinks about anything

4) https://t.co/vuhT6jVItx - Send notes that will self-destruct after being read.