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- const README: rewrite the space-saving claim per issue #5 follow-ups (constant-expression const vs #define immediates; which const qualify as constant expressions) - const README: fix the class-section diagnosis per issue #338 (overload resolution picks the const overload; the restriction only surfaces once that overload is removed) - sizeof README: virtual-inheritance result is compiler-dependent (GCC merges vbptr+vfptr -> 16, MSVC keeps them separate -> 32) #246 - static README: new section on internal linkage / access restriction with anonymous-namespace comparison #142 - 10-day practice: full problem list table + fixed day links #136 - new design_pattern/singleton/singleton_default.hpp: reusable thread-safe CRTP singleton template, compile+concurrency tested #303
70 lines
2.0 KiB
Markdown
70 lines
2.0 KiB
Markdown
> 来自 [C++那些事网站](https://light-city.github.io/stories_things/cpp-projects/cpp-short-url-demo/) 的文章，由站点同步脚本导出。
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# C++ 短链接服务 Demo
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真实的短链接相对来说比较复杂，例如：hash算法、放号系统等等。
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今天只是从小项目角度模拟一个短链接实现。
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如何通过短短的几十行代码快速实现一个？其中涉及的几个关键点：
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- 如何将长链接缩短
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- 如何存储映射关系
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映射关系就不用说了，整一个map持久化内存，如果涉及到数据库，需要通过数据库的jdbc/odbc等接口访问写入库当中。
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长链接缩短这里采用随机算法+固定长度思路来实现。
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## 1.随机
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通过uniform_int_distribution，生成一个`[a, b]`区间的随机数，这里随机从下列字符串中每次取一个字符，最后拼接起来就是短链接。
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```cpp
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string characters{
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"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"};
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```
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包含：
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- 数字
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- 小写字母
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- 大写字母
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```cpp
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uniform_int_distribution<int> distribution(0, characters.size() - 1);
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string code;
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for (int i = 0; i < length; ++i)
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code += characters[distribution(generator)];
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```
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## 2.存储
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每次将其存储到map中即可，例如：
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```cpp
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if (links.count(originalLink)) {
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return links[originalLink];
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}
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shortCode = generateRandomCode(len);
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string shortenedLink = base_url + shortCode;
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links[shortenedLink] = originalLink;
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```
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这里保留了基本url，例如：
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```cpp
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string baseUrl = "https://www.google.com.hk/search";
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LinkShortener shortener(baseUrl);
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string originalLink = "https://www.google.com.hk/search?q=asdsad&oq=asdsad&aqs=chrome.0.69i59j69i57j69i59l2.634j0j4&sourceid=chrome&ie=UTF-8";
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string shortenedLink = shortener.shortenLink(originalLink, 8);
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```
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最后便可以将这个url缩短为：
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```
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https://www.google.com.hk/searchtXuOlOSt
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```
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是不是很简单，本节的测试与完整代码已在星球更新，欢迎加入一起学习成长～ |