Forem: Hector Minaya

Find Duplicates in an Array

Hector Minaya — Fri, 11 Sep 2020 02:38:24 +0000

The Problem 🤔?

Write a function that will take in an array of integers and will return all duplicate elements.

Sample Dataset

let sampleData = [54,32,5,11,35,32,17,3,3,22,4,1,6,11];

Expected return

[ 32, 3, 11 ]

Approach #1 - Brute force

Let's create an Array to hold repeated elements.

    let repeatedElements = [];

Next we will loop over the array.

    // This is also known as O(n) in Big-O notation since
    // we have to iterate over all of the items in the array
    for(let i = 0; i < sampleData.length; i++) {

    }

Inside of the loop we will need to loop again and compare each integer to every other integer in the array to determine if they are duplicates.

    for(let i = 0; i < sampleData.length; i++) {
        // Added for clarity, not needed since we can access
        // sampleData[i] directly in our next loop.
        let item = sampleData[i];

        // Now we need to loop over the array again to see if
        // we find the same item again.
        // 
        // Unfortunately this adds O(n^2) complexity 😢
        for (ii = 0; ii < sampleData.length; ii++) {

            // Is it the same integer in a different position?
            if ( (item === sampleData[ii]) && (i !== ii) ) {

                // Add to our array so we can return.
                repeatedElements.push(item)
            }
        }
    }

Here is the full code 👇

let sampleData = [54,32,5,11,35,32,17,3,3,22,4,1,6,11];

function FindDuplicatesUsingBruteForce(sampleData) {

    let repeatedElements = [];

    for(let i = 0; i < sampleData.length; i++) {

        let item = sampleData[i];    
        for (ii = 0; ii < sampleData.length; ii++) {
            if ( (item === sampleData[ii]) && (i !== ii) ) {
                repeatedElements.push(item)
            }
        }
    }

    return repeatedElements;
}

console.log(FindDuplicatesUsingBruteForce(sampleData));

// returns: [ 32, 11, 32, 3, 3, 11 ]
// It actually returns items more than once, but
// I'll ignore this for now.

Be honest, at some point we've all written similar code 🤷‍♂️. This will get you the result we are looking for, but it's the slowest path that will take up the most resources 🤦‍♂️.

This is mostly due to the inner loop, it turns the algorithm into O(n^2).

If your dataset is small you won't notice the difference, but it will quickly slow down and 💣.

Don't use this approach 🛑.

Approach #2 - Using Arrays

Now let's try a slightly different approach, we will avoid the inner loop by using an extra array, which may or may not make this more efficient.

This extra array will keep track of the items that we have already seen.

    let uniqueElements = [];
    let repeatedElements = [];

Next up is the same loop as our first approach, which we will use for all other approaches.

    for(let i = 0; i < sampleData.length; i++) {

    }

Inside our loop we need to keep track of items we have already seen 👀.

    for(let i = 0; i < sampleData.length; i++) {

        // This is where it starts to get interesting. If
        // we have already seen this number we will add it
        // to our array of duplicated elements.
        //
        // What is the Big-O complexity of Array.includes?
        // I'll come back to this.
        if (uniqueElements.includes(sampleData[i])) {
            repeatedElements.push(sampleData[i]);
        }

    }

Plus new items 🔍.

    for(let i = 0; i < sampleData.length; i++) {

        if (uniqueElements.includes(sampleData[i])) {
            repeatedElements.push(sampleData[i]);
        } else {
            // Add to our unique elements to track items we have 
            // already seen
            uniqueElements.push(sampleData[i]);
        }

    }

Here is the full code 👇

let sampleData = [54,32,5,11,35,32,17,3,3,22,4,1,6,11];

function FindDuplicatesUsingArrays(sampleData) {

    let uniqueElements = [];
    let repeatedElements = [];

    for(let i = 0; i < sampleData.length; i++) {

        if (uniqueElements.includes(sampleData[i])) {
            repeatedElements.push(sampleData[i]);
        } else {
            uniqueElements.push(sampleData[i]);
        }

    }

    return repeatedElements;
}

console.log(FindDuplicatesUsingArrays(sampleData));

// returns: [ 32, 3, 11 ]

This seems more efficient than our previous approach and it may be, but it all depends on uniqueElements.includes 🤔.

Why? We are relying on the javascript implementation of includes which is a linear search of items in an Array.

If we go back to how data structures work we will remember that an array is very efficient O(1) if we look up an item by it's key/position, but terribly inefficient O(n) if we look up an item by it's value since we'll have to traverse the array until we find it's value 🤦‍♂️.

Is it more efficient than our first approach? Yes, but there are better ways to do this.

Bonus: An Array in javascript is not an Array 🙃.

Approach #3 - Using a Map()

What else can we try? What data structure has an O(1) lookup? A HashTable 😎.

    // As with a lot of things in JavaScript a Map isn't exactly a 
    // HashTable, but it's close enough for this problem.
    let uniqueElements = new Map();
    let repeatedElements = [];

Instead of uniqueElements.includes we will use the uniqueElements.has method of our Map.

    for(let i = 0; i < sampleData.length; i++) {

        // Since a HashTable lookup is O(1) we have greatly improved
        // our performance by just using a different data structure!!!
        if (uniqueElements.has(sampleData[i])) {
            repeatedElements.push(sampleData[i]);
        } else {
            uniqueElements.set(sampleData[i], sampleData[i]);
        }

    }

Here is the full code 👇

let sampleData = [54,32,5,11,35,32,17,3,3,22,4,1,6,11];

function FindDuplicatesUsingMap(sampleData) {

    let uniqueElements = new Map();
    let repeatedElements = [];

    for(let i = 0; i < sampleData.length; i++) {

        if (uniqueElements.has(sampleData[i])) {
            repeatedElements.push(sampleData[i]);
        } else {
            uniqueElements.set(sampleData[i], sampleData[i]);
        }

    }

    return repeatedElements;
}

console.log(FindDuplicatesUsingMap(sampleData));

// returns: [ 32, 3, 11 ]

So, how fast is this approach? Let's try and compare 👇

let sampleData = [];

// 50k array of random numbers
for (let i = 0; i < 50000; i++) {
    sampleData[i] = Math.floor((Math.random() * 50000) + 1);
}

/*
 Add here the 3 functions we just looked at
 */

// Let's run them all on the same array and time it.

console.time("FindDuplicatesUsingBruteForce");
FindDuplicatesUsingBruteForce(sampleData);
console.timeEnd("FindDuplicatesUsingBruteForce");

console.time("FindDuplicatesUsingArrays");
FindDuplicatesUsingArrays(sampleData);
console.timeEnd("FindDuplicatesUsingArrays");

console.time("FindDuplicatesUsingMap");
FindDuplicatesUsingMap(sampleData);
console.timeEnd("FindDuplicatesUsingMap");

Results 👇

Edit: There are dozens of different solutions to this problem, some more efficient in terms of space or time than the ones outlined here. If you'd like to share one please go ahead in the comments 👇

Offer to mentor someone in tech for the next few days

Hector Minaya — Thu, 12 Mar 2020 00:21:51 +0000

Liquid error: internal

Why did you leave your Boss?

Hector Minaya — Fri, 08 Nov 2019 16:23:00 +0000

The Wall Street Journal

@wsj

People don’t leave jobs, they leave managers. Survey finds half of workers have left a job because of the boss on.wsj.com/1IqZteO

12:26 PM - 02 Apr 2015

People have always said that their main reason for leaving their Job is their manager.

But we don't often get to hear the reasons behind it, without mentioning names/companies feel free to list some of the main reasons you've made the switch 👇

Don't throw away your old MBP, upgrade it!.

Hector Minaya — Thu, 07 Nov 2019 16:00:39 +0000

I have a Mid-2010 MBP that my kids use for homework, youtube and "stuff".

Back then Apple allowed you to swap out some of the internal components (HDD, RAM, Battery) and perform upgrades. If you still have one of these MBPs it's still worth it to do some small upgrades and get some more life out if.

So far I've done the following 👇

🧠 Upgraded RAM from 4GB to 16GB!
💾 Swapped out the 250 GB HDD for a 512GB Samsung EVO SSD
🔋 Replaced the original battery

The difference in terms of performance is huge, an SSD and 16GBs of RAM are worth it!.

Best of all, it's very simple to do, just open up the bottom cover and swap the parts, just like old times!.

If you need some guides to walk you through it head over to iFixIt, they cover pretty much everything.

For parts I usually compare between MacSales and Amazon. Getting quality parts through MacSales is usually better and not that expensive.

👨‍💻 DevToolList #2019 👩‍💻 - [Win10]

Hector Minaya — Wed, 06 Nov 2019 22:13:46 +0000

I have multiple laptops/environments where I code daily. I use a MBP, surface laptop, surface go and a mix of VMs.

Here is my go to list for tooling on a Windows Environment, updated for 2019 👇

🔨 Cascadia Code

This was released just over a month ago, but life is just so much easier when you have a nice font with ligatures enabled that you can use all over the place 😊🙌. I set it as the default font for all my IDEs, terminals, even Notepad!.

👉 https://github.com/microsoft/cascadia-code

🔨 Windows Subsystem for Linux (WSL)

For me, it's no longer Win vs Linux vs Mac. You need to have it all, and you need everything in the same place.

WSL has been one of the greatest additions to Windows for developers. Right now I'm using WSL 1, early next year we'll see a lot of improvements with WSL 2.

👉 https://docs.microsoft.com/en-us/windows/wsl/install-win10
👉 https://dev.to/hminaya/how-to-run-ruby-on-rails-with-windows-10-and-wsl-1-4he2

🔨 Git BASH

Git Wha? 🤔 Yeap. When dealing with Git on windows I use the Git Bash terminal, it's really cool and you can customize it heavily. This is how mine looks like 👇

👉 https://gitforwindows.org/

🔨 Windows Terminal

This could not come soon enough, finally we have a respectable terminal for Windows that we can customize and use everyday 👏

Check out some of Scott Hanselman's posts on how to setup your terminal with all of the cool stuff 👇

👉 https://www.hanselman.com/blog/NowIsTheTimeToMakeAFreshNewWindowsTerminalProfilesjson.aspx
👉 https://www.hanselman.com/blog/YouCanNowDownloadTheNewOpenSourceWindowsTerminal.aspx

🔨 Windows Power Toys

If you remember the original Power Toys, then yes, you too are getting old.

Hector Minaya

@hectorminaya

So, I guess I'm getting old, I do remember when we had Windows Power Toys

insider.windows.com/en-us/articles…

@windowsinsider

22:00 PM - 05 Nov 2019

It's still in preview, but it's great that they are bringing this back, I already using the Fancy Zones layout for my day to day workflow

👉 https://insider.windows.com/en-us/articles/announcing-the-first-preview-and-code-release-of-powertoys/

🔨 VS Code

Wow, there is so much to say about VS Code that I could write a whole series on it. Instead I'll just focus on the extensions that make my world run a lot smoother 🌎🤘.

✅ Remote Development - Connect to Docker Containers, SSH servers and WSL!
✅ Live Share - This is by far my favorite, it takes pair programming to a whole new level.
✅ Docker + Kubernetes - Manage my containers inside VSCode through a GUI
✅ GitLens - Git supercharged
✅ vscode-icons
✅ SQL Server (msssql)

🔨 Visual Studio 2019

Last, but not least, Visual Studio 2019. It's such a beast, there is no other IDE like it. Currently I enable the following workloads when installing 👇

✅ ASP.NET and web development
✅ Mobile development with .NET (Xamarin!)
✅ Azure develpment
✅ Node.js development
✅ Python development
✅ .NET desktop development
✅ Universal Windows Platform Development
✅ .NET Core cross-platform development

Feel free to leave your suggestions below in the comments.

How to make your ✨shiny new ASP.NET Core 3.0 API accessible from emulators and within your network 👀

Hector Minaya — Mon, 04 Nov 2019 22:15:49 +0000

You've just started a new project and decided you want to try out asp.net core 3.0 for your API 👏.

File -> New ... Run your API and you are instantly showered with JSON test data 👇

Great work 💪.

There is just one problem, if you are building this backend for a mobile app, you'll immediately run into that Aha moment, where you instantly remember that you can't access localhost from the emulator 👇

No problem, I'll just change "localhost" to the actual IP of my laptop and that will be the end of it 😎

Nop, nice try. That will get you one step closer, but now we are dealing with another problem 🙃.

What is going on 😔? The problem here is that IIS Express (used by default in VS2019) is only mapping requests for that port to "localhost".

Luckily this is very easy to fix 👇

1️⃣ Open up the .vs folder 📂

It is in the root of your solution. It's hidden by default, make sure to enable "Hidden items" in Explorer.

2️⃣ Fire up Visual Studio Code 🔥

Once inside, go to .vs[Your solution name]\config\ and find the applicationhost.config file. Open it up with VSCode.

3️⃣ Change the Bindings ⛓

Specifically we are looking for the bindings that are using the same port number and are pointing to localhost. It should look something like this 👇

        <bindings>
          <binding protocol="http" bindingInformation="*:53391:localhost" />
          <binding protocol="https" bindingInformation="*:44310:localhost" />
        </bindings>

Since this is our dev box, and we would like to make things easy on ourselves, I'm just going to change bindings to allow all.

        <bindings>
          <binding protocol="http" bindingInformation=":53391:" />
          <binding protocol="https" bindingInformation=":44310:" />
        </bindings>

4️⃣ It Works!!! 👏👏👏

Save, Re-launch your API and refresh the browser on your emulator!.

How to run Ruby on Rails with Windows 10 and WSL 1

Hector Minaya — Wed, 30 Oct 2019 02:44:39 +0000

Today I saw a twitter thread from DHH, which reminded me that even great developers struggle once in a while 👇

// Detect dark theme var iframe = document.getElementById('tweet-1188937316615610368-458'); if (document.body.className.includes('dark-theme')) { iframe.src = "https://platform.twitter.com/embed/Tweet.html?id=1188937316615610368&theme=dark" }

No, it's not that he bought a new Surface Laptop 3. It's that he was having trouble running Ruby on Rails on Windows 10 👇

// Detect dark theme var iframe = document.getElementById('tweet-1189304457894473732-694'); if (document.body.className.includes('dark-theme')) { iframe.src = "https://platform.twitter.com/embed/Tweet.html?id=1189304457894473732&theme=dark" }

🤔, he is human after all!.

Interestingly enough I saw a lot of people from Microsoft jump in the thread and try to help 👇

// Detect dark theme var iframe = document.getElementById('tweet-1189012830873255936-924'); if (document.body.className.includes('dark-theme')) { iframe.src = "https://platform.twitter.com/embed/Tweet.html?id=1189012830873255936&theme=dark" }
// Detect dark theme var iframe = document.getElementById('tweet-1188971490466680832-344'); if (document.body.className.includes('dark-theme')) { iframe.src = "https://platform.twitter.com/embed/Tweet.html?id=1188971490466680832&theme=dark" }

👏 Props to Rich Turner for providing some very useful tips 👏

// Detect dark theme var iframe = document.getElementById('tweet-1189262958800584704-66'); if (document.body.className.includes('dark-theme')) { iframe.src = "https://platform.twitter.com/embed/Tweet.html?id=1189262958800584704&theme=dark" }
// Detect dark theme var iframe = document.getElementById('tweet-1189297560315486209-604'); if (document.body.className.includes('dark-theme')) { iframe.src = "https://platform.twitter.com/embed/Tweet.html?id=1189297560315486209&theme=dark" }

Scott Hanselman shared a pretty good blog post about running RoR on Windows using WSL2. Which is fabulous!, but I would need to reformat my laptop, get on the windows insider (beta) fast ring, then enable WSL2.

Which as tempting as it may sound, I'm sure a lot of people don't want to commit their main laptop to a windows beta build.

Can you get this working right now, on your current Win10 install? Absolutely. I'll guide you through the process 👇

What are we going to use?

Win 10 | Version 1903 (Build 18362.449)
WSL 1
Visual Studio Code + Remote Developer Extensions

Step #1 - 👀 Make sure Win 10 is updated

Go to the search bar and type

winver

If you are running a version older than Version 1903 (Build 18362.449), go ahead and take the time to update windows, it will save you a lot of headaches 🧠.

Step #2 - 🔨 Install WSL1 + Ruby

Head over to the Microsoft Store and install your favorite version of Linux, In my case I'll use Ubuntu.

Once installed, just run the terminal and it will ask you to setup a username and pass 👇

⚠ Disclaimer #1: For the sake of brevity I'll take some shortcuts installing Ruby on Ubuntu, I do recommend installing RVM or rbenv and following proper protocol.*

First I'll install some prerequisites so I don't run into issues later on, just run the following commands 👇

sudo apt-get install software-properties-common
sudo apt-get install -y nodejs
sudo apt-get install gcc g++ make
sudo apt-get install libxml2-dev
sudo apt-get install libsqlite3-dev
sudo apt-get install yarn

Next, I'll just go ahead and install Ruby, you can use RVM or rbenv, but I'll keep it simple for this post 👇

After a few minutes you should have Ruby installed 👏. Now we'll install Rails to get an app running 👇

🎈🎊👏

Step #3 - 💻 Let's get VSCode running 🔥

Basically we are going to use VsCode to access the file system in WSL and make changes to our app.

⚠ Disclaimer #2: WSL1 and WSL2 are very different beasts. Follow the official Microsoft recommendations on where exactly to place your files. For now, I'm just trying to make the point of working in Windows while accessing the Ubuntu file system in WSL.*

So now, head over to VSCode and install the fabulous Remote Development Pack, this will enable you to open up the WSL filesystem and access the app you just created 👇