标签：#compute

leetcode.com Problem Statement Given the root of a binary tree, return its preorder traversal. Preorder Traversal follows: Root ↓ Left ↓ Right Brute Force Intuition In an interview, you can explain it like this: Visit the current node first, then recursively traverse the left subtree followed by the right subtree. Recursion naturally follows the preorder sequence. Complexity Time Complexity: O(N) Space Complexity: O(H) Where: N = Number of Nodes H = Height of Tree Recursive Code class Solution { public List < Integer > preorderTraversal ( TreeNode root ) { List < Integer > ans = new ArrayList <>(); preorder ( root , ans ); return ans ; } private void preorder ( TreeNode root , List < Integer > ans ) { if ( root == null ) return ; ans . add ( root . val ); preorder ( root . left , ans ); preorder ( root . right , ans ); } } Moving Towards the Optimal Iterative Approach Instead of recursion, we can use a stack. Since preorder visits: Root ↓ Left ↓ Right we should process the root immediately. To ensure the left subtree is processed first, push the right child before the left child . Pattern Recognition Whenever you see: Preorder Traversal Simulate Recursion Think: Stack Key Observation Stack follows: LIFO To visit: Left First push: Right First ↓ Left Second so that left is popped first. Optimal Java Solution class Solution { public List < Integer > preorderTraversal ( TreeNode root ) { List < Integer > ans = new ArrayList <>(); if ( root == null ) return ans ; Stack < TreeNode > st = new Stack <>(); st . push ( root ); while (! st . isEmpty ()) { TreeNode node = st . pop (); ans . add ( node . val ); if ( node . right != null ) st . push ( node . right ); if ( node . left != null ) st . push ( node . left ); } return ans ; } } Dry Run 1 / \ 2 3 / \ 4 5 Stack: 1 Visit: 1 Push: 3 2 Visit: 2 Push: 5 4 Traversal: 1 ↓ 2 ↓ 4 ↓ 5 ↓ 3 Answer: [1,2,4,5,3] Why Stack Works? A stack processes the most recently added node first. By pushing: Right Child ↓ Left Child the left child

The second word a professor told me to carry for life. It took me years — and a lot of vectors — to start understanding it. A look back — long before any of the tools we argue about now. The same professor — Sang Lyul Min — handed us these words one at a time in lecture. After trade-off , two more stuck with me. But before the second word itself, here are the two pieces of news he brought to class around then. The internet barely existed; information moved through journals, magazines, and word of mouth. Looking back, it's a little amazing how much still got through. When a chess machine started winning The first breakthrough I remember: computers had finally started playing chess on roughly even terms with the world's best. Deep Blue beat Kasparov around 1996, so the machines he was describing came just before — names like Deep Thought, ChessMachine, Socrates II. He told us, deadpan, that one human competitor's head had "physically burst" from the strain — and we groaned, "Come on, Professor, that's a bit much." We live on the far side of AlphaGo now, so it's easy to forget how much we shrugged at all this back then. I was a decent amateur — a 1-dan at Go, hopeless at janggi (Korean chess) against any program — and I still remember the hollow, slightly bitter feeling the AlphaGo era left even in someone who only ever played for fun. A full-body scan The second: in the US, death-row inmates had consented to the first dense full-body image scans. That was the news that taught me — embarrassingly late — that this kind of computing could reach all the way into medicine. Computers, it turned out, showed up in the strangest places. orthogonal Back to the words. The second one, the professor said, would run through my whole career: orthogonal . The Korean rendering — 직교하는, "at right angles" — was, naturally, a word I'd never heard. The plain-language version was "unrelated, independent." It came back hard years later, when I had to take vectors seriously — first in linear

But the system would require a massive leap from any of its existing hardware.

The Chinese supercomputer LineShine was ranked as the fastest in the world, despite not using any GPUs.

Eight kids, eight chairs, one rule: explaining FIFA's best-thirds draw to my 8-year-old Rahul Devaskar Rahul Devaskar Rahul Devaskar Follow Jun 27 Eight kids, eight chairs, one rule: explaining FIFA's best-thirds draw to my 8-year-old # webdev # soccer # math # worldcup Add Comment 14 min read

Operating system, a thing that everybody uses but no one talks about. While reading Operating Systems: Three Easy Pieces (OSTEP), my background in C and C++ fueled a growing fascination with memory allocation, virtualization, scheduling, and the intricate mechanics of operating systems. This would be a series of article, the number i am not sure, it will be the amount of content that someone might comfortably read in a 10 min Article. Keeping each piece to a solid 10-minute read is the perfect sweet spot for a developer to read over a cup of coffee. It gives you enough runway to explain a core concept, show the math, and link a practical C/C++ experiment without making their eyes glaze over. Why this Article ? We are often warned against “reinventing the wheel.” However, I firmly believe that building and optimizing modern software is impossible without a fundamental grasp of virtualization, memory allocation, and concurrency. Consider Docker: it functions almost entirely on OS-level virtualization features like Namespaces, cgroups, and isolated filesystems. Similarly, the highly optimized Memory Manager in PostgreSQL only works because it leverages the robust memory management systems already written into the OS kernel. This article aims to bring the core concepts of OSTEP to life through practical experimentation. By accompanying the theory with an open-source repository, my goal is to provide a clear, interactive learning experience that demystifies operating systems. I am not an operating system guru or a Principal Engineer with years of experience, but I hope to become one someday (assuming AI doesn’t replace me first… HeHe ). What I can do is dive in, explore, and try to understand these concepts by actually building things. Because of that, my goal here is to present the findings and experiments I explore rather than giving strong opinions — I’ll leave the comment section for those! Any support, feedback, or contributions from the community will be incredibly

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Lately, it feels like my feed is completely flooded with "Become an AI/ML Engineer in 2 Hours!" crash courses and quick certificates promising a golden fast-track into machine learning roles. But let’s be completely real for a second: there are no tutorial shortcuts here. The more I dive into actual system architecture and cloud infrastructure, the more obvious it becomes: machine learning isn't a standalone magic trick. It's built entirely on rock-solid Computer Science, efficient data structures, and heavy-duty software engineering. Software Engineering First, AI Second If you can’t build or scale a reliable backend, manage data pipelines, or understand low-level underlying system logic, you simply cannot scale an AI model in production. Prompt engineering is cool for prototyping, but production-level ML requires real, foundational engineering skills. You have to learn how to be a great software engineer first. Looking Past the Hype (A Solid Structural Roadmap) If you actually want to look past the superficial fluff and understand how real data workloads, model deployments, and ML infrastructure fit into a cloud environment, I found an incredibly solid, structured resource. Instead of hand-waving past the hard parts, Microsoft Learn has an official, step-by-step breakdown on Azure AI and Machine Learning Fundamentals. It actually goes into the core architectural principles and shows you what real cloud-scale infrastructure looks like. Whether you are trying to map out your summer learning roadmap or just want to understand the actual systems backing these models, I highly recommend checking it out. Here is the structured entry point if you want to skip the shortcuts and dive into the real infrastructure: 🔗 Official Azure Machine Learning Technical Hub What are your thoughts? Are you seeing the same "AI shortcut" hype on your feeds, or are people finally starting to focus back on core system fundamentals? Let's discuss in the comments!

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Math.random() returns a number between 0 and 1, and roughly nobody reading this could explain what happens between the call and the return. That is fine, fine right up until the output decides who gets money, and then it becomes one of the genuinely hard problems in applied software, the kind that regulated industries build entire testing labs around. Start with the thing most people get wrong: a sequence that passes for random and a fair sequence are different claims, and your users cannot tell them apart by staring at outputs. The users will never catch the difference and that is the whole problem in one sentence. This is why fairness in any real-money system, an online casino being the sharpest example, is a verification problem long before it is a math problem. Pseudorandom generators are deterministic. A PRNG eats a seed, runs it through fixed arithmetic, and spits out numbers that sail through statistical randomness tests while being completely predetermined by that seed. Mersenne Twister is the poster child: excellent distribution, used everywhere by default for years, and from a few hundred observed outputs you can reconstruct its internal state and predict the rest. For a Monte Carlo simulation, who cares! For anything where a human has a financial reason to guess your next number, you just shipped a vulnerability and called it a feature. What you want when stakes exist is a CSPRNG. The guarantee that matters: even with a long history of outputs, an attacker cannot compute the next one or recover the internal state. crypto.randomBytes() in Node. crypto.getRandomValues() in the browser. They sit one autocomplete away from the unsafe option and offer wildly different guarantees, which is exactly why this bug ships so often. The safe call and the dangerous call look like fraternal twins. ** The part players actually rely on ** Say you build it correctly: a proper CSPRNG, real entropy, no timestamp nonsense. You know it is fair but now prove it to a stranger wh

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Network-attached storage (NAS) provides accessible shared space on your home network. After testing, these are my favorite NAS devices.