Algorithms, Blockchain and Cloud

Turn Your Raspberry Pi into a Family Network Drive: 2TB WD Hard Drive Setup for Kids’ Macs

ACMer — Thu, 02 Oct 2025 13:21:46 +0000

“Create a 2TB Network Drive with Raspberry Pi for Your Family” “Raspberry Pi + WD Hard Drive: Easy Network Storage for Kids’ Macs” “Family File Sharing Made Easy: DIY Raspberry Pi Network Drive” “Turn a Raspberry Pi into a 2TB Shared Hard Drive for Home” “Save Space on Your Kids’ Macs with a Raspberry Pi Network Drive” A couple of years ago, I bought a MacBook Pro for each of my two kids. My younger son’s laptop cost around $600 at the time and had only a 256GB SSD, so the storage often filled up. He constantly had to delete Continue Reading »

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Microsoft Shareholders Reject Proposal to Add Bitcoin to Balance Sheet

ACMer — Mon, 29 Sep 2025 11:15:13 +0000

Every year, I receive a letter from Microsoft because I own a few shares of Microsoft stock (RSUs), which also makes me a shareholder. The letter invites me to attend Microsoft’s annual shareholder meeting and lists several resolutions to be discussed, including recommendations from shareholders, such as Vote or Deny. In the last letter I received, one of the items was about whether to include Bitcoin on the company’s balance sheet. Unfortunately, Microsoft’s shareholders voted against this proposal. At Microsoft’s annual shareholder meeting on December 10, 2024, shareholders overwhelmingly voted against a proposal to include Bitcoin on the company’s balance Continue Reading »

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Chessly (British Short Hairs) Classified as Persian Cat by ResNet-50

ACMer — Fri, 26 Sep 2025 19:29:47 +0000

Chessly is one of my cat, she is a British shorthairs. However, she has been categorized as a Persian Cat by the ResNet-50 Image Classification Model. Introduction to ResNet-50 ResNet (Residual Network) was proposed by Microsoft Research in 2015. It solves the degradation problem in deep neural networks through residual structures. ResNet-50 is one of the commonly used versions, with a total of 50 layers. Core Idea The residual block is computed as: This shortcut connection helps avoid gradient vanishing and makes deeper networks easier to train. Network Structure The input image size is usually 224×224. Main stages: 7×7 convolution Continue Reading »

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A Complete Guide to Radix Sort in Python with Examples

ACMer — Mon, 22 Sep 2025 10:16:34 +0000

Python Radix Sort Tutorial: Sorting Integers, Negatives, and Floats A Complete Guide to Radix Sort in Python with Examples Python Sorting Algorithms: Radix Sort Explained Efficient Number Sorting in Python Using Radix Sort Radix Sort in Python: From Positive Integers to Floats Introduction to Radix Sort in Python Radix Sort is a non-comparative sorting algorithm that works by sorting numbers digit by digit. Instead of comparing entire numbers directly, it distributes elements into “buckets” based on their digits or characters, and processes one digit position at a time. For integers, Radix Sort typically works from the least significant digit (LSD) Continue Reading »

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A Complete Guide to Sorted Data Structures in Python

ACMer — Mon, 22 Sep 2025 09:18:14 +0000

Ordered data structures are very useful in programming, especially in algorithm competitions and competitive programming. In Python, the Sorted Containers library mainly provides three such data structures: SortedDict, SortedSet, and SortedList. Mastering Python’s Sorted Data Structures: From Built-ins to sortedcontainers A Complete Guide to Sorted Data Structures in Python When and How to Use Sorted Lists, Dicts, and Sets in Python Python Sorted Data Structures Explained with Real-World Examples Sorted Containers vs Built-ins: The Python Developer’s Guide to Ordered Data Python Sorted Data Structures Tutorial Sorting is one of the most common operations in programming. Python provides several ways to Continue Reading »

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How would you do Binary Search to Locate a Block given a TimeStamp (for Any Blockchain)?

ACMer — Fri, 19 Sep 2025 19:36:03 +0000

A couple of days ago, I wanted to look up the block numbers of some important records on the STEEM blockchain — such as when I: registered my account #4253590 became a witness #20190755 mined my first block #20390040 was delegated SP by Justin Sun #41676911 and received a DAO payout #95403889 I only knew the timestamps but not the exact block numbers, so I thought of using Binary Search to locate them. It is definitely doable. However, sometimes it might be quicker to use the **SDS API**, since this information can be retrieved by a simple query against the Continue Reading »

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This Year’s Microsoft’s Hackathon

ACMer — Wed, 17 Sep 2025 19:55:26 +0000

This week, I joined Microsoft’s Hackathon for the first time. In fact, big tech companies like Microsoft, Amazon, and Meta all host Hackathons every year—it’s part of their culture. Microsoft’s Hackathon usually takes place in September and lasts three days. Engineers and researchers can freely form teams to work on fun projects around the themes of “Build” and “Hack.” Three days isn’t enough to build a full product, so the focus is on creating a prototype, and at the end, teams submit a video for evaluation. Last year, there was also a Hackathon, but it wasn’t company-wide and had no Continue Reading »

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Microsoft’s Excel Just Got Smarter: The New Copilot Function

ACMer — Thu, 21 Aug 2025 20:38:38 +0000

All in AI. Microsoft has integrated AI (Copilot) to its Office products. I’m thrilled to share that Excel has added COPILOT directly into formulas! =COPILOT(prompt,,…) This deceptively simple syntax brings the power of large language models (LLMs) into your spreadsheet logic—unlocking a whole new era of financial planning, analysis, and data modeling. Why It’s a Game-Changer for FP&A and Data Analysis FP&A stands for Financial Planning & Analysis. It’s like the company’s “financial brain,” responsible for helping management plan how money is spent, forecast future income and expenses, analyze the company’s financial health, and provide decision-making advice to help the Continue Reading »

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How to Set Up and Test a WebSocket Server in Python with Existing CLI Tools?

ACMer — Fri, 08 Aug 2025 11:09:56 +0000

Introduction to WebSockets WebSockets enable real-time, full-duplex communication between clients and servers over a single TCP connection. In this post, we’ll show you how to set up a simple WebSocket server in Python and how to test it using both a Python client and popular command-line utilities like websocat and wscat. Setting Up a WebSocket Server in Python We’ll use the websockets library, which provides an easy-to-use asyncio-based WebSocket server implementation. Here’s a simple server (in Python) that listens on port 9090 and prints any received messages with timestamps: import asyncio import websockets from datetime import datetime async def handler(websocket): Continue Reading »

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The latest Raspberry Pi 5 comes with up to 16GB of RAM, but it’s a bit pricey.

ACMer — Wed, 06 Aug 2025 20:47:41 +0000

Raspberry Pi: One of the Most Iconic Tech Symbols in the UK From Cambridge to Home Servers: The Charm and Future of Raspberry Pi Visiting the Raspberry Pi Physical Store and Prospects of a DAO Project A British Pride: Raspberry Pi and Its Innovative Uses In the UK, besides Rolls-Royce engines, London’s financial institutions, Oxford and Cambridge University, and the traditional fish and chips, Raspberry Pi is probably one of the most famous things. The only physical Raspberry Pi store in the whole UK is located in the Grand Arcane shopping center in Cambridge. Every time I go shopping there Continue Reading »

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Telegram Accounts Are Shockingly Easy to Hack Without 2FA

ACMer — Mon, 04 Aug 2025 20:32:20 +0000

“How My Telegram Account Got Hacked—and What I Learned” “A Cautionary Tale: Telegram Security and 2FA” “Why You Must Enable 2FA on Telegram Immediately” “Telegram Accounts Are Shockingly Easy to Hack Without 2FA” “Don’t Make My Mistake: Telegram Without 2FA Is a Time Bomb” “99% of Hacked Telegram Accounts Have This in Common” “Telegram Security: Lessons from a Close Call” “I Trusted Telegram Too Much—Until My Account Got Hacked” My Telegram account was hacked last week, but fortunately, no damage was done. I mainly use Telegram to watch videos, and there’s no sensitive information in it. I also enabled two-factor Continue Reading »

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Fundamental mathematical formulas for machine learning (optimization): argmax Reasoning Backward from the Future

ACMer — Tue, 29 Jul 2025 18:01:59 +0000

argmax: Reasoning Backward from the Future The fundamental mathematical principle behind all of machine learning (and optimization) is the following formula: arg_max_{x∈X} F(x) It means: among all possible inputs , find the one that maximizes the objective function F(x). The result of this expression is the optimal input x, not the maximum value itself. This formula represents the idea of reasoning backward from the future to make the best choice now. The space of all possible x’s is often unenumerable, and the function F is usually unknown ahead of time—it’s something we try to learn or approximate. This reflects a Continue Reading »

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Why NordVPN Is the Best Choice for Online Privacy and Security in 2025

ACMer — Mon, 28 Jul 2025 13:37:04 +0000

In today’s digital world, where our personal data is constantly at risk and internet restrictions are tightening across the globe, a reliable VPN has become an essential tool. One of the most trusted names in the VPN industry is NordVPN?—a powerful and feature-rich service designed to protect your privacy, secure your connection, and unlock the full potential of the internet. Whether you’re streaming, gaming, working remotely, or simply browsing, NordVPN? offers a premium experience that makes staying safe online both easy and fast. So, what exactly is NordVPN? Simply put, NordVPN? is a Virtual Private Network (VPN) service developed by Continue Reading »

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Python match vs Traditional if-elif: A Modern Take on Switch Statements

ACMer — Wed, 23 Jul 2025 17:39:54 +0000

In Python, the match keyword is used for pattern matching, introduced in Python 3.10 as part of structural pattern matching, similar to switch statements in other languages, but far more powerful. Introduction What is the match Keyword? Starting from Python 3.10, the match statement introduces structural pattern matching. It acts like a powerful switch statement found in many other languages, but with far more expressive capabilities. Basic Example Using match def handle(value): match value: case 1: print("One") case 2: print("Two") case _: print("Something else") This works similarly to a switch-case statement in C or JavaScript, but allows for much more Continue Reading »

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Auditing blockchain wallet code with Copilot AI

ACMer — Sat, 19 Jul 2025 18:25:48 +0000

I found that AI can be very useful for auditing code security. For example, I had been using a wallet extension that supports STEEM and Blurt, but it suddenly stopped working. Normally, I clone the source code from GitHub and load the extension locally using the “Load Unpacked Extension” option in Chrome. This method is safer because it avoids the risk of malicious code being introduced during automatic Chrome extension updates — such as secretly uploading users’ private keys. The reason the extension stopped working this time is that Chrome no longer supports extensions built with Manifest V2. Although there Continue Reading »

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Understanding the LEA Instruction: A Powerful Tool for Address Calculation in x86 Assembly

ACMer — Wed, 16 Jul 2025 20:28:39 +0000

What Is the LEA Instruction? In x86 assembly, the LEA (Load Effective Address) instruction is used to **compute the address** of a memory operand and store it in a register — **without accessing memory**. It is commonly used for pointer arithmetic and offset calculations. Basic Syntax LEA destination, source destination: Must be a register (e.g., eax, ebx, etc.) source: A valid memory address expression, like Practical Example lea eax, Assume: ebx = 1000 ecx = 3 Then the instruction does: eax = 1000 + 3 * 4 + 8 = Continue Reading »

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C++ Forward References: The Key to Perfect Forwarding

ACMer — Tue, 15 Jul 2025 20:27:57 +0000

In modern C++ (C++11 and beyond), a powerful feature called forward references enables developers to write flexible, efficient, and generic functions that handle both lvalues and rvalues — with just a single template declaration. Despite their confusing syntax, forward references are essentially a neat syntactic mechanism that makes your code both concise and high-performance. What Is a Forward Reference? A forward reference happens when a template parameter is used in a function parameter as T&&, and T is deduced. For example: template<typename T> void func(T&& arg); This may look like an rvalue reference, but it’s a forward reference because T Continue Reading »

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PHP7.x is deprecated by WordPress: Why You Should Upgrade to PHP8.x?

ACMer — Mon, 14 Jul 2025 09:57:43 +0000

Time to Say Goodbye to PHP 7.4 — My Blogs Are Finally Getting an Upgrade After Years on PHP 7.4, It’s Finally Time to Upgrade to 8.x PHP 7.4 No Longer Supported — Blog Upgrades on the Agenda The “If It Works, Don’t Touch It” Days Are Over — Time to Upgrade PHP WordPress Warning: PHP 7.4 Is Outdated, Time for Me to Act Your site is running on an outdated version of PHP (7.4.33), which does not receive security updates. It should be updated. What is PHP and how does it affect my site? PHP is one of the Continue Reading »

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How to Clean Up NVM Node Versions Except One?

ACMer — Sun, 13 Jul 2025 21:28:34 +0000

How to Remove All NVM Node.js Versions Except One NVM is Node Version Manager, which can be installed via github. With NVM, one can easily manage and installs multiple versions of Node/NPM on the same server. Use Case You’re using nvm (Node Version Manager) to manage multiple Node.js versions You want to clean up your system and keep only one version: v22.16.0 Step 1: List All Installed Node Versions nvm ls Step 2: Use Bash to Uninstall All But One Replace the KEEP_VERSION with the version that you want to keep. The following BASH script removes/uninstalls all versions expect the Continue Reading »

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Last Month’s Scam Experience on Telegram (NordVPN Impersonation)

ACMer — Sat, 12 Jul 2025 18:31:13 +0000

Last month, someone claiming to be a NordVPN employee (Salbatore Isom) contacted me on Telegram. He said he was part of NordVPN’s Influence Program and wanted to collaborate with me. At first, I ignored him. Later, I casually replied. He explained that I only needed to pin a post on X (formerly Twitter) for a week and retweet it once per week. In return, I’d receive $1,000 per month, paid in cryptocurrency—70% upfront, and the remaining 30% at the end of the month. He said the USDT payment could be made on TRON, ETH, or SOL chains. I didn’t suspect Continue Reading »

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Bitcoin has reached All-Time-High 118K

ACMer — Fri, 11 Jul 2025 19:41:04 +0000

Bitcoin has reached an all-time high of $118,000, and the core driver behind this surge is the synchronized recovery of institutional buying and overall market risk appetite. After months of caution, institutions are once again increasing their exposure to digital assets, signaling renewed confidence in crypto as an investable asset class. This rebound in institutional demand has aligned with a broader return of risk-on sentiment across financial markets, creating a strong upward momentum for BTC. Another key factor fueling the rally is the growing expectation that the U.S. Federal Reserve is entering a more accommodative monetary policy phase. Investors anticipate Continue Reading »

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Teaching Kids Programming – Number of Equivalent Domino Pairs (Hash Table + Combination)

ACMer — Tue, 08 Jul 2025 15:02:10 +0000

Teaching Kids Programming: Videos on Data Structures and Algorithms Given a list of dominoes, dominoes = is equivalent to dominoes = if and only if either (a == c and b == d), or (a == d and b == c) – that is, one domino can be rotated to be equal to another domino. Return the number of pairs (i, j) for which 0 <= i < j < dominoes.length, and dominoes is equivalent to dominoes. Example 1: Input: dominoes = ,,,] Output: 1 Example 2: Input: dominoes = ,,,,] Output: 3 Constraints: 1 <= Continue Reading »

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Turning a Dusty Raspberry Pi into a Home Server for Blockchain Monitoring

ACMer — Sat, 05 Jul 2025 21:51:47 +0000

TLDR; I’ve now 27 servers, and some are low-cost or even free. For example, oracle gives you 2 free VMs, and I run a raspberry pi 4b home. I run microservices on small VMs. I put raspberry pi in a shoe closet, connect it to router. and I overclocked the CPUs from 1.4 GHz to 2.2 GHz, the temperature stays between 30 to 40 degrees with 2 fans. Re-using the Raspberry PI 4b as a mini server I have three or four Raspberry Pi devices at home, most of which have been gathering dust. One of them is an all-in-one Continue Reading »

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Understanding dynamic_cast in C++: Safe Downcasting Explained

ACMer — Tue, 01 Jul 2025 21:19:41 +0000

What Is dynamic_cast in C++? Purpose Safely convert between polymorphic types at runtime Commonly used to downcast from a base class to a derived class Performs a runtime type check using RTTI (Run-Time Type Information) Basic Syntax Derived* d = dynamic_cast<Derived*>(basePtr); If basePtr points to an actual Derived object, the cast succeeds If not, the result is nullptr When It Fails Pointer cast: returns nullptr if the actual type is not the target Reference cast: throws std::bad_cast on failure Pointer Downcast Example class Entity { virtual ~Entity() {} }; class Player : public Entity {}; class Enemy : public Entity Continue Reading »

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Monitoring 28 VPS Machines (Including a Raspberry Pi) with Nezha Dashboard

ACMer — Tue, 24 Jun 2025 19:43:07 +0000

Side Projects and My Fleet of 28 Servers Over the years, I have worked on various small projects—blogs, online tools, and being a STEEM witness. Currently, I manage 28 servers. Most are budget VPS instances, and the newest is a Raspberry Pi 4B installed in my home shoe cabinet. Tracking Server Info in Excel Each server’s static information—IP, VPS provider, memory, storage—is documented in an Excel sheet. Automated Monitoring via Cron Scripts I wrote numerous Bash scripts that run periodically using Crontab. These scripts detect: Disk usage exceeding thresholds CPU overloading If something goes wrong, I receive an email alert Continue Reading »

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The Halting Problem and Its Paradoxical Cousins: When Logic Looks at Itself

ACMer — Thu, 19 Jun 2025 18:25:44 +0000

The Halting Problem: Can a Program Predict Itself? Problem: Given a program P and input x, can you determine whether P(x) halts or loops forever? Introduced by Alan Turing in 1936 Proved to be undecidable — no algorithm can solve it for all inputs Involves self-reference: Can a program analyze another program, including itself? Turing’s Thought Experiment Assume: H(P, x) tells whether P(x) halts Define the Following Python Code: def D(P): if H(P, P): while True: pass # loop forever else: return 0 # halt Then what happens with D(D)? If D(D) halts, then it must loop forever If D(D) Continue Reading »

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Compute GCD in Bash with Input Validation

ACMer — Wed, 18 Jun 2025 21:23:53 +0000

GCD Computation in Bash What is GCD? GCD stands for Greatest Common Divisor. It is the largest positive integer that divides two numbers without leaving a remainder. For example: GCD of 8 and 12 is 4 GCD of 14 and 49 is 7 GCD is useful in simplifying fractions, cryptographic algorithms, and number theory. Algorithms to Compute GCD 1. Euclidean Algorithm The most common and efficient method. Based on the principle that gcd(a, b) = gcd(b, a % b). Repeat until b becomes 0. At that point, a is the GCD. 2. Subtraction-Based Algorithm Keep subtracting the smaller number from Continue Reading »

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What is Moravec’s Paradox?

ACMer — Wed, 11 Jun 2025 18:04:18 +0000

What is Moravec’s Paradox? Moravec’s Paradox is a significant observation in the fields of artificial intelligence and robotics. One-sentence summary “Tasks that are easy for humans are often extremely difficult for machines; tasks that are hard for humans are often easy for machines.” Origin of the Paradox Proposed in the 1980s by Hans Moravec, Rodney Brooks, Marvin Minsky, and others They observed that while computers can easily handle logical reasoning, they struggle with perception and motor skills: tasks like advanced mathematics, chess, and logical inference are relatively easy for machines; but tasks like perceiving the world and moving like humans Continue Reading »

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Why a Leading Space in Linux Shell Commands Can Matter?

ACMer — Thu, 05 Jun 2025 19:28:36 +0000

Understanding the Leading Space Behavior in Linux Shells Overview In Linux shell environments like bash, prefixing a command with a space can influence whether or not that command is saved to your command history. This subtle trick is useful when working with sensitive data or when you simply don’t want a command logged. The Key Variable: HISTCONTROL The behavior is controlled by a shell environment variable called HISTCONTROL. To see your current setting, run: echo $HISTCONTROL For example, you might see: ignoredups:ignorespace Explanation of Values Option Description ignoredups Prevents duplicate consecutive commands from being saved to history. ignorespace Prevents commands Continue Reading »

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Teaching Kids Programming – Fibonacci Numbers in (Generate Binary Strings Without Adjacent Zeros)

ACMer — Wed, 04 Jun 2025 21:46:10 +0000

Teaching Kids Programming: Videos on Data Structures and Algorithms You are given a positive integer n. A binary string x is valid if all substrings of x of length 2 contain at least one “1”. Return all valid strings with length n, in any order. Example 1: Input: n = 3 Output: Explanation: The valid strings of length 3 are: “010”, “011”, “101”, “110”, and “111”. Example 2: Input: n = 1 Output: Explanation: The valid strings of length 1 are: “0” and “1”. Constraints: 1 <= n <= 18 Understanding the Fibonacci Pattern in Valid Binary Strings Continue Reading »

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C vs C++: Understanding the restrict Keyword and Its Role in Compiler Optimization

ACMer — Wed, 04 Jun 2025 21:03:31 +0000

What is restrict in C? The restrict keyword was introduced in C99 as a type qualifier for pointers. It tells the compiler that the pointer is the only means by which the memory it points to will be accessed for the duration of its lifetime. This allows the compiler to safely optimize code by assuming no aliasing — meaning no other pointer accesses the same memory. Syntax Example: void copy(int *restrict dst, const int *restrict src, size_t n); Benefits: Enables more aggressive compiler optimizations Improves performance in tight loops and memory-heavy operations Clarifies developer intent about pointer usage Without restrict: Continue Reading »

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ROS Topics, Services, and Actions Explained with Clear Examples

ACMer — Wed, 04 Jun 2025 20:15:50 +0000

It is said that the next ten years will be the era of Robotics with AI (Artificial Intelligence). “ROS – Robot Operating System The Robot Operating System (ROS) is a set of software libraries and tools that help you build robot applications. From drivers to state-of-the-art algorithms, and with powerful developer tools, ROS has what you need for your next robotics project. And it’s all open source.” Introduction to ROS and ROS 2 ROS (Robot Operating System) is a flexible framework for writing robot software. It provides tools, libraries, and conventions to simplify the task of creating complex and robust Continue Reading »

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C++: lvalue, rvalue and rvalue references

ACMer — Thu, 29 May 2025 22:08:48 +0000

C++ lvalue, rvalue, and rvalue references Understanding lvalues, rvalues, and rvalue references is essential for mastering modern C++ features like move semantics and perfect forwarding. 📌 What is an lvalue? An lvalue refers to a location in memory — it has a name and can appear on the left-hand side of an assignment. int x = 10; x = 20; // x is an lvalue int* p = &x; // can take address of x 📌 What is an rvalue? An rvalue is a temporary object or value that does not have a persistent memory address. It typically appears on Continue Reading »

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C++ assert vs static_assert

ACMer — Wed, 28 May 2025 21:30:25 +0000

C++ assert vs static_assert C++ provides two mechanisms to enforce assumptions: assert and static_assert. Though they seem similar, they operate at very different stages and serve distinct purposes. 🔍 assert — Runtime Check assert verifies conditions at runtime. If the condition is false, it prints an error and aborts execution. #include <cassert> int divide(int x, int y) { assert(y != 0); // Aborts if y is 0 return x / y; } assert is typically used in debug builds and is disabled when NDEBUG is defined. 🧱 static_assert — Compile-Time Check static_assert checks conditions during compilation. If the condition fails, Continue Reading »

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Why auto_ptr is deprecated in C++?

ACMer — Tue, 27 May 2025 18:40:43 +0000

Why auto_ptr is deprecated in C++ TLDR; the auto_ptr smart pointer keyword has been deprecated in C++ 11 and removed in C++ 17. Deprecation and Removal std::auto_ptr was deprecated in C++ 11. It was completely removed in C++ 17. Why Was auto_ptr Deprecated? It had unsafe copy semantics. Copying an auto_ptr transferred ownership and left the source as nullptr. This behavior led to bugs, especially when used in STL containers or standard algorithms. <code>std::auto_ptr<int> p1(new int(42)); std::auto_ptr<int> p2 = p1; // Ownership transferred std::cout << *p2 << std::endl; // OK std::cout << *p1 << std::endl; // Undefined behavior (p1 is Continue Reading »

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C++ what is the consteval? How is it different to const and constexpr?

ACMer — Sat, 24 May 2025 18:25:36 +0000

C++: What is consteval? How is it Different from const and constexpr? If you’ve been using const and constexpr in your C++ code, you might be wondering what the new consteval keyword in C++20 brings to the table. Let’s break it down clearly. What is consteval? The consteval specifier declares a function as an immediate function, meaning the function must be evaluated at compile time. Unlike constexpr, which allows both compile-time and runtime evaluation, consteval enforces compile-time only. consteval int square(int x) { return x * x; } Any attempt to call this function with non-constant input (or at runtime) Continue Reading »

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Tutorial on C++ std::move (Transfer Ownership)

ACMer — Sun, 18 May 2025 20:50:58 +0000

📘 C++ Move Semantics & std::move() Tutorial C++ std::move() is used to transfer the ownership of a variable/object. 🔹 What is Move Semantics? In C++, move semantics optimize performance by transferring ownership of resources (like memory or file handles) instead of copying them. Move semantics were introduced in C++11, and they allow: Faster transfers of large or expensive-to-copy objects More efficient use of temporary values 🔹 What is std::move()? std::move(x) does not move anything — it simply casts x to an rvalue reference (i.e., T&&), telling the compiler: “You can treat this object as a temporary and move from it.” Continue Reading »

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const vs constexpr in C++

ACMer — Sat, 17 May 2025 14:48:40 +0000

C++ const vs constexpr: What’s the Real Difference? Both are used in C++ to define constants. Why This Matters Modern C++ encourages writing immutable, efficient, and expressive code. Two keywords—const and constexpr—sit at the heart of that effort. They look similar, but understanding their distinct guarantees is crucial for clean compile‑time and run‑time behavior. High‑Level Comparison Feature const constexpr Compile‑time constant? Maybe Always (or fails to compile) Runtime OK? Yes Yes (evaluated at runtime if needed) Array/template usage Only if truly constant Guaranteed Functions allowed? Only qualifiers on member Full functions evaluable at CT 1 Declaring Immutable Data const: Immutable After Continue Reading »

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Tutorial on C++ Ranges

ACMer — Sat, 17 May 2025 13:59:02 +0000

C++20 introduced ranges, a powerful and elegant abstraction for working with sequences (like arrays, vectors, etc.). Ranges improve readability, composability, and performance compared to raw iterators or old-style loops. What Are Ranges? A range in C++20 is an abstraction that represents a sequence of elements that can be iterated over. It pairs well with views and actions like filtering, transforming, and more. Traditional vs Range-based loop #include <iostream> #include <vector> int main() { std::vector<int> v = {1, 2, 3, 4}; // Old-style loop for (auto it = v.begin(); it != v.end(); ++it) std::cout << *it << ' '; // Range-based Continue Reading »

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Tutorial on C++ Smart Pointers

ACMer — Thu, 15 May 2025 21:44:43 +0000

Tutorial on Smart Pointers in C++ Smart pointers in C++ provide automatic and safe memory management. They help avoid memory leaks and dangling pointers by ensuring proper object destruction through RAII (Resource Acquisition Is Initialization). This tutorial covers the three primary smart pointers in C++: std::unique_ptr std::shared_ptr std::weak_ptr 1. std::unique_ptr unique_ptr has exclusive ownership. Only one unique pointer can own a resource at a time. Example: Owning a Simple Object #include <iostream> #include <memory> int main() { std::unique_ptr<int> p = std::make_unique<int>(42); std::cout << "Value: " << *p << "\n"; // Transfer ownership std::unique_ptr<int> q = std::move(p); if (!p) std::cout << Continue Reading »

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From Idea to GitHub Pages: Building Tools with AI and Vibe Coding

ACMer — Thu, 15 May 2025 16:01:34 +0000

Built and Open-Sourced A Few Mini Tools with AI Recently, I used ChatGPT-4o and o4-mini to quickly build and open-source a few handy tools (100% client based, local/javascript). The motivation was simple—every time I needed to convert YAML/JSON or do Base64 encoding, I found myself Googling for some online tools. Then I thought, why not just build my own? At the same time, I’ve been learning frontend development with React, so it felt like the perfect opportunity to put that into practice. So I basically played the role of a product manager—gave my requirements to ChatGPT, and it quickly set Continue Reading »

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Toss a Coin 256 Times: The Math Behind an Unbreakable Bitcoin Private Key

ACMer — Thu, 24 Apr 2025 18:55:47 +0000

Why Cracking a Bitcoin Key Is Harder Than You Can Possibly Imagine I often see some brute-force programs constantly trying to crack Bitcoin wallet keys, claiming they’ve been lucky enough to stumble upon the keys to a few wallets and moved tens of thousands of dollars from them. Toss a Coin 256 Times, and You Have a Bitcoin Private Key: A Cryptographic Miracle Beyond Human Computation Cracking Bitcoin requires the power of 4 billion galaxies? Ordinary people simply cannot fathom this mathematical abyss. If you assign 1 to heads and 0 to tails, and toss a coin 256 times in Continue Reading »

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BASH: How to Get HTTP Response Code using Curl Command?

ACMer — Thu, 17 Apr 2025 21:12:17 +0000

To check the HTTP response code after running a curl command, you can use the -w option with curl, which allows you to specify a custom output format. Here’s the command: curl -o /dev/null -s -w "%{http_code}\n" <URL> You can save the HTTP response code into a BASH variable, like this: resp=$(curl -o /dev/null -s -w "%{http_code}\n" <URL>) Explanation: -o /dev/null: Discards the output of the response body. -s: Runs curl in silent mode (no progress or error messages). -w “%{http_code}\n”: Outputs only the HTTP response code. Replace <URL> with the actual URL you’re checking. How to Get HTTP Response Continue Reading »

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Teaching Kids Programming – Compute the Range Sum with Update: A Deep Dive into Segment Tree, SQRT Decomposition, Brute Force & Prefix Sum

ACMer — Sat, 12 Apr 2025 21:47:35 +0000

Teaching Kids Programming: Videos on Data Structures and Algorithms When working with arrays, one common task is to compute the sum of elements within a range, along with supporting dynamic updates to the array values. While a brute-force solution may work for small datasets, as the array grows, efficient techniques become crucial. In this post, we’ll walk through four different approaches to solve the range sum with updates problem: Brute Force Prefix Sum Square Root Decomposition (SQRT) Segment Tree Each method has its strengths and trade-offs in terms of time complexity, implementation difficulty, and real-world use cases. Compute the Range Continue Reading »

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Building a Reliable Witness Vote Checker for the Steem Blockchain (with Retry & Exponential Backoff)

ACMer — Mon, 07 Apr 2025 14:53:49 +0000

When working with decentralized platforms like Steem, it’s important to expect occasional hiccups — network issues, API rate limits, or temporary downtimes. That’s why any integration, bot, or tool you build should be able to fail gracefully and recover smartly. In this post, I’ll walk you through a simple yet robust vote-checking utility for the Steem blockchain that: First Version: Check a Witness voted by Here’s a handy Node.js function that checks if a Steem user has voted for a specific witness — either directly or via a proxy. function is_voted_by(witness, id) { return new Promise((resolve, reject) => { steem.api.getAccounts(, Continue Reading »

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AI Transforms Photos into Ghibli Style? ChatGPT-4o Costs Money, But Here’s a Free Method!

ACMer — Sun, 30 Mar 2025 10:56:06 +0000

Generate Ghibli Style Photos via Using the Image to Image Feature (Grok 3) These past few days, Ghibli-style images have flooded social media, from WeChat Moments to X (Twitter). Even Elon Musk posted about this new feature in ChatGPT-4o. It feels like, overnight, AI has become capable of replacing most designers’ jobs. This AI image editing feature (strictly speaking, image-to-image generation) is only available in the paid version of ChatGPT-4o, which costs $20 per month. I subscribed to ChatGPT Plus/Pro for six months two years ago, but my account was later banned due to payment issues—I was using a OneKey Continue Reading »

The post AI Transforms Photos into Ghibli Style? ChatGPT-4o Costs Money, But Here’s a Free Method! first appeared on Algorithms, Blockchain and Cloud.

Why does the exchange force liquidation when the margin is low?

ACMer — Sat, 22 Mar 2025 17:12:07 +0000

In the cryptocurrency market, as long as you don’t trade contracts, the risk is not very high. I have never traded contracts because I think trading contracts is essentially gambling. I’m not sure whether there are leveraged futures products in the stock market, but in the cryptocurrency market, due to less regulation, you can apply leverage to some futures (Futures) with several times the leverage. What is leverage? Simply put, leverage is a tool that allows you to use a small amount of capital to control a larger amount of capital. For example, if Bitcoin is currently $100, but you Continue Reading »

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How to Repeat Until Errors using GDB or LLDB Debugger?

ACMer — Thu, 20 Mar 2025 18:46:44 +0000

How to Repeat Until Errors using GDB or LLDB Debugger When debugging programs, it’s common to want to repeatedly run a program until it encounters an error. Both GDB (GNU Debugger) and LLDB (LLVM Debugger) offer ways to automate this process. Let’s dive into how to set this up in each debugger. This is particular very useful to debug the flakey programs e.g. some tests when the tests may fail randomly or rarely crashed with SegFault e.g. Segmentation fault (or Bus Error). Introduction: GDB vs LLDB GDB (GNU Debugger) and LLDB (LLVM Debugger) are powerful tools for debugging applications at Continue Reading »

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Using Docker to Run Firefox as a Proxy: A Simple Solution for Accessing Blocked Websites in China

ACMer — Sat, 08 Mar 2025 16:23:48 +0000

When I was travelling to China, the most annoying thing is accessing foreign websites: Gmail, YouTube videos, etc. In mainland China, “using a VPN” is illegal, but it seems that in major cities like Shanghai and Beijing, permits need to be obtained for using VPN legally. For example, some international companies and government institutions can apply to bypass the Great Firewall (GFW). One easy option is to use the paid VPN services. This post shows how to set up a Firefox Browser on a server using a simple docker command. Running Firefox Browser in a Docker Container Assuming your host/server/VPS Continue Reading »

The post Using Docker to Run Firefox as a Proxy: A Simple Solution for Accessing Blocked Websites in China first appeared on Algorithms, Blockchain and Cloud.

When Your PC Slows Down, It Might Be Time for an Update

ACMer — Sat, 08 Mar 2025 09:36:55 +0000

I use a Microsoft Surface Studio as my daily workstation and rarely shut it down or restart it unless Windows forces an update. Recently, the entire OS became sluggish, with Chrome freezing the system when loading pages with large tables. At first, I tried closing unnecessary applications and clearing some memory, but the issue persisted. Even simple tasks, like switching between windows or opening the Start menu, felt laggy. Eventually, I decided to reboot, which immediately triggered the installation of pending updates. After the reboot, everything returned to normal—Chrome no longer froze, and the overall system performance improved significantly. It Continue Reading »

The post When Your PC Slows Down, It Might Be Time for an Update first appeared on Algorithms, Blockchain and Cloud.

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