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#pragma once的作用

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#pragma once 作用： 1. 当一个头文件被多个源文件或其他头文件直接或间接 #include 时，该指令能确保它只被编译一次。 2. 避免宏名冲突：传统的 #ifndef 保护需要为每个文件设计独特的宏名（如 __MY_HEADER_H__）， 若不小心在不同文件用了相同的宏名会导致代码失效；而 #pragma once 基于物理文件路径，彻底避免了命名污染和冲突。 3. 书写简洁：只需在头文件最上方写一行即可，无需写 #ifndef、#define 和 #endif 4 与#ifndef的区别： 4.1 标准性：#ifndef 是 C++ 标准支持的传统方法（也称 Include Guard）； 而 #pragma once 虽然是非标准指令，但现代绝大多数主流编译器（如 GCC、Clang、MSVC）都提供了完美支持。 4.2 控制粒度：#ifndef 可以防范同一文件内局部的 代码片段 重复，而 #pragma once 只能针对 整个物理文件 。
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Strategy Pattern

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  Comparison of Modern C++ Approaches Implementation Type Mechanism Resolution Time Memory Overhead Use Case Runtime (Functional) std::function & Lambdas Runtime Small heap allocation (if lambda captures exceed small-buffer optimization) When algorithms must change on the fly during program execution. Compile-time (Static) Templates & Concepts ( requires ) Compile-time Zero runtime overhead (inlines perfectly) High-performance systems where strategies are known at compile time. Example 1: #include <bits/stdc++.h> class SortingStrategy { public: virtual void sort(std::vector<int>& arr) = 0; }; class BubbleSort : public SortingStrategy { public: void sort(std::vector<int>& arr) override { // Implement Bubble Sort algorithm } }; class QuickSort : public SortingStrategy { public: void sort(std::vector<int>& arr) override { // Implement Quick Sort algorithm } }; // Add more sorting algorithms as ne...
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Flyweight Pattern

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The Flyweight design pattern is a structural pattern designed to minimize memory usage by sharing as much data as possible with other similar objects. It divides an object's data into two categories: intrinsic state(heavy, constant, and shareable data) and extrinsic state (lightweight, unique, context-specific data) #include <iostream> #include <string> #include <string_view> #include <unordered_map> #include <vector> #include <memory> #include <shared_mutex> // 1. INTRINSIC STATE (The Flyweight) // This class contains heavy, immutable data shared across thousands of instances. class TreeModel { public: TreeModel(std::string name, std::string color, std::vector texture_data) : name_(std::move(name)), color_(std::move(color)), texture_bytes_(std::move(texture_data)) { std::cout texture_bytes_; // Simulates heavy mesh/texture data }; // 2. FLYWEIGHT FACTORY // Manages the shared pool of flyweights. It ensures obje...
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Design Patterns

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Creational: Factory Method (class) Abstract Factory (object) Builder  (object) Prototype  (object) Singleton  (object) Structral: Adapter (class/object) Bridge (object) Composite (object) Decorator  (object) Facade  (object) Flyweight   (object) Proxy  (object) Behavioral: Interpreter (class) Template Method (class) Chain of Responsibility (object) Command (object) Iterator (object) Mediator (object) Memento (object) Observer (object) State (object) Strategy (object) Visitor (object)
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Adding Chinese watermarks to images using ffmpeg on Windows 10

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Code: ffmpeg -i i1.jpg -vf "drawtext=text='仅为开户使用':fontfile='C\:/Windows/Fonts/msyh.ttc':fontsize=168:fontcolor=white@0.5:x=(w-text_w)/2:y=(h-text_h)/2" output.jpg Multi Line Version: ffmpeg -i i1.jpg -vf "drawtext=text='仅为开户使用':fontfile='C\:/Windows/Fonts/msyh.ttc':fontsize=w*0.03:fontcolor=white@0.7:x=w*0.1:y=h*0.2,drawtext=text='仅为开户使用':fontfile='C\:/Windows/Fonts/msyh.ttc':fontsize=w*0.03:fontcolor=white@0.7:x=w*0.4:y=h*0.2,drawtext=text='仅为开户使用':fontfile='C\:/Windows/Fonts/msyh.ttc':fontsize=w*0.03:fontcolor=white@0.7:x=w*0.7:y=h*0.2,drawtext=text='仅为开户使用':fontfile='C\:/Windows/Fonts/msyh.ttc':fontsize=w*0.03:fontcolor=white@0.7:x=w*0.1:y=h*0.5,drawtext=text='仅为开户使用':fontfile='C\:/Windows/Fonts/msyh.ttc':fontsize=w*0.03:fontcolor=white@0.7:x=w*0.4:y=h*0.5,drawtext=text='仅为开户使用':fontfile='C\:/Windows/Fonts/msyh.ttc':fontsize=w*0.03:fontcolor=white@0.7:x...
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Using spdlog in a C++ project

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Tree structure of the project. The code of main.cc. #include <iostream> #include "spdlog/spdlog.h" #include "spdlog/sinks/basic_file_sink.h" #include "spdlog/sinks/rotating_file_sink.h" void do_work_in_another_file(); void rotating_example() { try { // Create a file rotating logger with 5 MB size max and 3 rotated files auto max_size = 1048576 * 5; auto max_files = 3; // Set output time pattern // %f: Time accurate to microseconds // %n: Output mode "some_logger_name" // %l: Prints the severity level of the log message. Example include info, warn, error, debug or critical. // %v: Prints the actual text or payload of the log message that you passed to the function. spdlog::set_pattern("[%Y-%m-%d %H:%M:%S.%f] [%n] [%l] %v"); // Set it as default so you can spdlog::info() directly. auto logger = spdlog::rotating_logger_mt("som...
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vim的智能配置

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" 显示行号 set number " 将Tab键自动转换为空格 set expandtab " 设置Tab键本身的宽度为4个空格 set tabstop=4 " 设置按退格键(BackSpace)时一次删除4个空格 set softtabstop=4 " 设置使用>或<进行缩进时的宽度为4个空格 set shiftwidth=4 " 开启自动缩进(新行继承上一行的缩进) set autoindent " 开启C/C++语言智能缩进 set cindent " 搜索优化 set incsearch set ignorecase " 语法高亮 syntax on " 开启256色支持(在终端使用时非常重要) set t_Co=256
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