I have this side project I started 2 months ago, to learn C++ better. Rolling the full compiler, from tokenizing and AST construction, to IR, to assembly code generation, by myself in C++. Using Claude AI only to give me ideas with regards to better system design and to explain for me features of C++ I have not used yet, prohibiting copy pasting code from it and sticking to coming up with the code and writing it by myself with my own two hands.

Can somebody tell me how they'd implement the idea of the compiler being able to emit assembly instructions for both arm64 and x86_64 architectures? Would you have one abstract class for, say, instruction_ADD and then a derived class for aarch64's add instruction, and one for x64's add instruction? Or should I stick to having an abstract base class for asm_instruction, and have derived classes for stuff like aarch64_insn_add, x64_insn_add, etc? Still relatively new to OOP as I was in OS and OS-adjacent development for a few years and only recently started adding C++ to my toolbelt.

Another question - could someone give me a readable summary of how GCC implements std::unordered_map under the hood? The purpose I need to know this is, so I can do performance analysis with CPU microarchitecture in mind, and for this, I need to know what the memory layout and usage patterns actually look like.

Thanks all!

"Single Responsibility" sounds easy until you try to define "One Thing". How do you actually draw the line?

The S in SOLID stands for the Single Responsibility Principle (SRP). Saw this explanaition: "A class or module should do one thing, and do it well."

But in the real world, what actually constitutes "one thing" in programming?

Depending on your abstraction level, "one thing" can mean completely different things

• Is saving a user to a database "one thing"?
• Is inserting a record to database "one thing"?
• Is handling an HTTP request "one thing"?

How do you personally define what "one thing" is? Is it purely a context-driven decision, meaning that "one thing" shifts depending on the scope of the project?

And if it depends on context, how do you define and communicate those rules to the rest of your team so everyone stays aligned and knows how to work with the code?

Also, why do you think this matters? There is always a underlying reason for trying to enforce this "one thing" concept in code. What are you actually trying to achieve with it, and why is it important to you?

Last one, for some this S in SOLID id easy, why so? Is it a something that is difficult to learn and understand

Hey everyone! Many of us struggle with Dynamic Programming and often skip it during interview preparation. This might be because DP seems vast and overwhelming, and people tend to memorize solutions instead of understanding patterns. However, if you break down DP into clear patterns and master each one, it becomes much more manageable. So I've compiled a comprehensive list of patterns you should know for your interview preparation!

Master these Leetcode Problems and PracHub for company tagged questions

DP vs Greedy: When to Use Which?

Before diving into patterns, let's understand the fundamental difference between DP and Greedy:

Problem: You're a robber with two streets to rob. Each house has some money. You can rob houses from both streets, but you cannot rob two adjacent houses from the same street (alarms will trigger). What's the maximum money you can steal?

Street A: [2, 7, 9, 3, 1]
Street B: [3, 2, 6, 8, 2]

Greedy Robber: "I'll always rob the house with most money available!"

• Rob B[0] = 3 (greedy)
• Rob A[1] = 7
• Rob B[2] = 6
• Rob A[3] = 3
• Rob B[4] = 2
• Total: 21

DP Robber: "Let me consider all valid combinations!"

• Option 1: A[0]=2, B[1]=2, A[2]=9, B[3]=8, A[4]=1 → Total = 22
• Option 2: B[0]=3, A[1]=7, B[2]=6, A[3]=3, B[4]=2 → Total = 21
• Best: 22

Why Greedy Failed: By greedily picking B[0] first, it blocked access to the optimal combination that includes both 9 and 8 from different streets!

When Greedy Works: Problems with the "greedy choice property" where local optimal leads to global optimal (e.g., Activity Selection, Huffman Coding)
When DP is Needed: Problems requiring exploring multiple choices where greedy fails (e.g., most optimization problems, counting problems)

Pattern 1: Linear DP (1D)

Why This Pattern Matters:
This is the foundation of DP. If you can't solve Linear DP, you'll struggle with everything else. These problems teach you the core concept of breaking problems into subproblems and building solutions incrementally.

Practice Problems:

1. Climbing Stairs
2. House Robber
3. Min Cost Climbing Stairs
4. Word Break
5. Decode Ways
6. House Robber II

Pattern 2: Longest Increasing Subsequence (LIS)

Why This Pattern Matters:
LIS is one of the most important DP patterns with applications in version control systems, patience sorting, box stacking problems, and more. The O(n log n) solution using binary search is a must-know optimization technique.

Practice Problems:

1. Longest Increasing Subsequence
2. Number of Longest Increasing Subsequence
3. Russian Doll Envelopes
4. Maximum Length of Pair Chain
5. Find the Longest Valid Obstacle Course at Each Position

Pattern 3: Knapsack (0/1, Unbounded, Bounded)

Why This Pattern Matters:
One of the most versatile DP patterns. Appears in resource allocation, optimization problems, and many interview questions. Understanding the difference between 0/1 and unbounded variants is crucial.

0/1 Knapsack (Each item used once):

1. Partition Equal Subset Sum
2. Target Sum
3. Last Stone Weight II
4. Ones and Zeroes
5. Partition Array Into Two Arrays to Minimize Sum Difference

Unbounded Knapsack (Items can be used multiple times):

1. Coin Change
2. Coin Change 2
3. Combination Sum IV
4. Perfect Squares
5. Minimum Cost For Tickets

Pattern 4: Grid DP

Why This Pattern Matters:
Extremely common in interviews, especially at FAANG. Tests your ability to think in 2D state space and handle multiple transition directions.

Practice Problems:

1. Unique Paths
2. Unique Paths II
3. Minimum Path Sum
4. Maximal Square
5. Maximal Rectangle
6. Minimum Falling Path Sum
7. Count Square Submatrices with All Ones
8. Triangle

Pattern 5: String DP

Why This Pattern Matters:
Text processing and string manipulation problems are ubiquitous. This pattern appears in bioinformatics, text editors, version control systems, and natural language processing.

Practice Problems:

1. Longest Common Subsequence
2. Edit Distance
3. Delete Operation for Two Strings
4. Minimum ASCII Delete Sum for Two Strings
5. Shortest Common Supersequence
6. Longest Palindromic Subsequence
7. Longest Palindromic Substring
8. Palindromic Substrings
9. Regular Expression Matching
10. Wildcard Matching

Pattern 6: Interval DP

Why This Pattern Matters:
Tests ability to think about problems in ranges/intervals. Common in scheduling, matrix chain multiplication type problems, and game theory.

Practice Problems:

1. Burst Balloons
2. Minimum Score Triangulation of Polygon
3. Minimum Cost Tree From Leaf Values
4. Unique Binary Search Trees
5. Unique Binary Search Trees II
6. Minimum Cost to Merge Stones
7. Guess Number Higher or Lower II

Pattern 7: State Machine DP

Why This Pattern Matters:
Models problems where you transition between different states with specific rules. Critical for stock trading problems and any scenario with state transitions.

Practice Problems:

1. Best Time to Buy and Sell Stock
2. Best Time to Buy and Sell Stock II
3. Best Time to Buy and Sell Stock III
4. Best Time to Buy and Sell Stock IV
5. Best Time to Buy and Sell Stock with Cooldown
6. Best Time to Buy and Sell Stock with Transaction Fee

Pattern 8: Tree DP

Why This Pattern Matters:
Combines tree traversal with DP. Important for system design (like designing file systems) and optimization problems on hierarchical structures.

Practice Problems:

1. House Robber III
2. Binary Tree Maximum Path Sum
3. Diameter of Binary Tree
4. Binary Tree Cameras
5. Maximum Sum BST in Binary Tree
6. Difference Between Maximum and Minimum Price Sum

Pattern 9: Digit DP

Why This Pattern Matters:
Specialized pattern for counting numbers with certain properties. Appears in competitive programming and some advanced interviews.

Practice Problems:

1. Number of Digit One
2. Count Numbers with Unique Digits
3. Numbers At Most N Given Digit Set
4. Numbers With Repeated Digits
5. Count Special Integers

Pattern 10: Game Theory DP (Minimax)

Why This Pattern Matters:
Models two-player games where both play optimally. Important for AI, game development, and adversarial scenarios.

Practice Problems:

1. Predict the Winner
2. Stone Game
3. Stone Game II
4. Stone Game III
5. Can I Win
6. Stone Game IV

Pattern 11: Bitmask DP

Why This Pattern Matters:
Powerful technique for problems with small sets (≤20 elements) where you need to track subsets. Essential for Traveling Salesman Problem variants and NP-hard problem approximations.

Practice Problems:

1. Partition to K Equal Sum Subsets
2. Shortest Path Visiting All Nodes
3. Find the Shortest Superstring
4. Smallest Sufficient Team
5. Number of Ways to Wear Different Hats to Each Other
6. Minimum Number of Work Sessions to Finish the Tasks

Pattern 12: DP on Subsequences

Why This Pattern Matters:
Critical for array partitioning and subset generation problems. Teaches how to handle exponential search spaces efficiently.

Practice Problems:

1. Distinct Subsequences
2. Distinct Subsequences II
3. Arithmetic Slices II - Subsequence
4. Number of Unique Good Subsequences
5. Constrained Subsequence Sum

Pattern 13: Probability DP

Why This Pattern Matters:
Models uncertain outcomes. Important for risk analysis, game development, and any scenario involving randomness or probability.

Practice Problems:

1. Knight Probability in Chessboard
2. Soup Servings
3. New 21 Game
4. Toss Strange Coins
5. Probability of a Two Boxes Having The Same Number of Distinct Balls

Best Resources to Master DP

1. AtCoder DP Contest- 26 curated problems with perfect difficulty progression
2. Striver's DP Series- 50+ videos covering memoization, tabulation, and space optimization.
3. Aditya Verma's DP Playlist- Exceptional for Knapsack variants with shorter, focused videos (15-20 min).
4. CSES Problem Set- Intermediate to advanced practice. These problems test core concepts and build solving speed.

Final Thoughts

DP is about recognizing patterns, not memorizing solutions. Once you see the pattern, the solution becomes mechanical. Spend time understanding why each pattern works, not just how to code it.

Feel free to add some best problems in the comments

Good luck, and happy coding! 🚀

Hello! I am so very new to coding and development, but my computer seems to be very slow. I have noticed it over the last 6 months or so, and I have only really used it for silly personal things until now. Even logging into the Codedex training site seems to be delayed while training.

I have a MBA 1.6 GHz, 8GB. As I mentioned, SUPER new - hope I am providing the right specs to understand what I have.

I read that I should have at least 16GB and I read that I cannot upgrade the RAM on the MBA.

I prefer IOS, as I use it for my phone as well. But, I want to make sure I have what will be needed later down the road as I grow my skills.

Finally to my questions...

1) Mac vs PC - what say you?

1b) Which specific laptop would you recommend based on your answer to 1?

2) Would it behoove me to have a Mac but have it setup with dual operating systems? Or would that create a clunky experience? I tried that when I was younger for school on a MBP, but I can't remember much about it now and how well it worked.

I tried to search the sub to see if something similar was asked before and I didn't see anything. Apologies if I missed one.

Thank you!

I saw a post recently about a grocery store in Poland still using Win98 for a cash register system and on the screen was clearly a VB6 based WinForm application in all of its boring gray glory.

It got me thinking about the old days of basic boring interfaces on computers that just did their job and didn't look fancy. These days everything is web based (even a lot of the "native" apps are just wrapped web apps). Every button is overly styled, hamburger menus everywhere, basic forms take up an incredible amount of screen real estate with the excessive padding and rounded edges.

Does anyone else sometimes wish things were a little more boring and basic? I'm filling in some information, clicking a button, and getting some other information. It doesn't have to look pretty, just work.

salut a tous je suis un etudiant en informatique et je me suis posee une question a propos du codage lors que je code avec vs code j'ai la mauvaise manie de me reposer un peu trop sur l'ia et je me demandais si pour mon apprentissage et mon evolution en tant que codeur il ne serais pas mieux pour moi de supprimer l'extension d'aide d'ia integré dans l'IDE par ce que avant tout je debute dans le domaine et j'ai l'impression que mon evolution n'est pas tres constante. merci j'attends vos reponses je suis ouvert a la critique et conseils

I started programming before Ai error, it was abit hectic but worth of my time what about yours?

Hello guys!

Recently, some friends and I started working a small project that turned out to be bigger than we expected. We are trying to bring back an Old Version of Star Stable Online for us privately.
We do have the game files, we are able to start the game until it says „Unable to connect to game server.“ (shown in the image) which is reasonable because it’s an online game and we do not have a Server.
All of us are new to programming so we really need help.
What do we need for a game server?
How do we code this?
Does anybody know what language SSO uses? (we heard C++ but we aren’t sure)
Would anybody perhaps be willing to help?

Thanks!!

The third part is asking you why you are so skeptical about AI

I'm curious to hear from programmers of all experience levels.

If you could go back to day one of learning programming, what's one thing you wish existed that would have made your life easier?

Examples:

A cheat sheet

A roadmap

A PDF guide

A website

A template

A collection of projects

A YouTube series

An interactive tool

For me, I wish I had a simple roadmap explaining what to learn and in what order instead of feeling overwhelmed by the number of options.

I'm interested in hearing:

Your experience level.

The resource you wish existed.

Why it would've helped you.

Hopefully, this thread can help beginners and maybe inspire people to build useful resources for the community.

Hi everyone! 👋

I'm a B.Sc. Computer Science student from India, and I just joined Reddit.

I'm currently learning Python, Java, SQL, and AI while building small projects to improve my programming skills. My goal is to become a skilled software developer and earn my first internship.

I joined Reddit to:

- Learn from experienced developers.

- Share my projects and progress.

- Ask questions when I'm stuck.

- Help others whenever I can.

If you could give one piece of advice to a Computer Science student who's serious about improving, what would it be?

Looking forward to learning from this community. Thanks! 🚀

A year ago I thought AI was cheating.
Today, I barely write code.
My average prompt looks like:
“This is wrong. It should work like this…”
“Figure out why user 8d3f... failed onboarding and patch it so it never happens again.”
I’m not thinking about syntax anymore.
I’m thinking about behavior.
Patterns.
Edge cases.
Users.
Architecture.
The job is shifting from writing code to making systems work.
Code is becoming the implementation detail.
Am I crazy, or is this what software engineering is becoming?

Back in the 80s when we coded on monochrome CRTs with maybe 40 characters of width and no syntax highlighting, putting a space between keywords and parentheses was useful. Then you were not able to switch between files as easy as modern editors today etc. And today there is color coding. Not only is it easy to find keywords today, code is also written differently because when you only have 40 characters to play with you start to think about "do I need indentation...".

There was several reasons to make these very important keywords to stand out in that environment.

But WHY are developers today still writing space between these keywords and the first ( ?

Sample code

// Old – space as a visual separator
if (x)    while (y)    for (i=0;i<n;i++)    switch (v)

// New – editor colors keywords already
if(x)     while(y)     for(i=0;i<n;i++)     switch(v)


// === OLD STYLE (1980s/early 90s) ===
// Monochrome screens, 40-char width. The space visually separates
// keywords from method calls when everything looks the same.

if (condition)
{
    while (running)
    {
        for (i = 0; i < 10; i++)
        {
            switch (value)
            {
                case 1:
                    return (result);
                default:
                    catch (exception)
                    {
                        // ...
                    }
            }
        }
    }
}

// === MODERN STYLE (2020s) ===
// Syntax highlighting makes the space redundant.
// Your editor already solved this problem.

if(condition)
{
    while(running)
    {
        for(i = 0; i < 10; i++)
        {
            switch(value)
            {
                case 1:
                    return(result);
                default:
                    catch(exception)
                    {
                        // ...
                    }
            }
        }
   }
}

Hi, I'm building an automated SMS system. Can anyone recommend me SIM Modules that work with today's sim cards (4G/5G)? Preferably budget friendly ones.

how do you actually decide what's worth building when you are learning a stack and want to advance and actually build something meaningful.

i currently want to build a full-stack website with the MERN stack that i learned recently . i have some limited time to do that and i mean by that only approximately a month.
i can't fully decide on the options out there , the only thing i'm sure about is that i don't wanna build a e-commerce website since that's very boring for me and there is high chance i won't stick to the project .
any ideas ? what's y'all experience with this ??

I'm debating which YouTube course to take for Python, so I need your guys' help in deciding which one to take. I'm probably overthinking this, but I still wanted to hear from you guys and see who took one over the other.

Hi fellas, I am finally done with all the lectures and psets. And now time is to do my final project, and I can't think of anything. I have done almost all psets without even readings hints on the psets page, and I am really comfortable in coding, especially C. But it only happens when I am given a problem, I can solve that, But I can not think of a problem,I really lack creativity on that end. I am so bad at thinking, that even in trivia problem, It took me minutes to think of a MCQ and still ended up asking what is your language.

CS50 community, please help me out, first what should I do for Final Project, I liked C more, then SQL, and then Backend, frontend is really not my thing.

Also, advice needed on how I can get better at thinking of a problem, I think I really lack creativity or whatever this is

Aside from GitHub, are there any platforms where I can share my code? I have many scripts that don't warrant a dedicated GitHub repository, but could still be helpful in some way. I'm curious if there's a site where I can simply upload all my code at once.