bit | 易学教程

bit operation AND

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问题 It is a leetcode problem. Given an array of numbers nums, in which exactly two elements appear only once and all the other elements appear exactly twice. Find the two elements that appear only once. For example: Given nums = [1, 2, 1, 3, 2, 5], return [3, 5]. My code is: class Solution { public: vector<int> singleNumber(vector<int>& nums) { int axorb=0; for(auto i:nums) axorb=axorb^i; int differbit=(axorb&(axorb-1))^axorb; int group3=0, group5=0; for(auto i:nums) if(differbit&i!=0) group5

Where to learn about “bit”?

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问题 I am trying to find some books or resources talking about bit in detail so that for example I would be able to translate a number (like 16) into bits. I am currently a high school student and whenever reading a programming books I can understand almost everything except the bit/bitwise operators part. I just do not know how it works and why do people even invent bit & byte :(. Therefore, I hope that you guys can give me some resources suggestions talking about how to translate number

Changing bits in an int in C?

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问题 So I have a 16 bit number. Say that the variable name for it is Bits. I want to make it so that Bits[2:0] = 001, 100, and 000, without changing anything else. I'm not sure how to do it, because all I can think of is ORing the bit I want to be a 1 with 1, but I'm not sure how to clear the other bits so that they're 0. If anyone has advice, I'd appreciate it. Thanks! 回答1: To clear certain bits, & with the inverse of the bits to be cleared. Then you can | in the bits you want. In this case, you

Is there a currently used system with a C++ compiler where int is over 32 bits wide?

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问题 C++ standard says only that int has to be at least 16 bits wide . And at least according to cppreference, it's almost always either 16 or 32 bits wide: data model int width in bits ---------------------------------- C++ standard at least 16 LP32 16 ILP32 32 LLP64 32 LP64 32 ... Other models are very rare. For example, ILP64 (8/8/8: int, long, and pointer are 64-bit) only appeared in some early 64-bit Unix systems (e.g. Unicos on Cray). Is there an example of a currently used system with a C++

Write one single bit to binary file using BinaryWriter

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问题 I want to write one single bit to a binary file. using (FileStream fileStream = new FileStream(@"myfile.bin", FileMode.Create)) using (BinaryWriter binaryWriter = new BinaryWriter(fileStream)) { binaryWriter.Write((bool)10); } Something like binaryWriter.Write((bit)1); When I use binaryWriter.Write((bool)1) the file has one byte, but I want to write one single bit. Is this possible? 回答1: You cannot store only 1 bit in a file. Almost all modern filesystems and hardware store data in segments

详解布隆过滤器的原理，使用场景和注意事项

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什么是布隆过滤器本质上布隆过滤器是一种数据结构，比较巧妙的概率型数据结构（probabilistic data structure），特点是高效地插入和查询，可以用来告诉你 “某样东西一定不存在或者可能存在” 。相比于传统的 List、Set、Map 等数据结构，它更高效、占用空间更少，但是缺点是其返回的结果是概率性的，而不是确切的。实现原理 HashMap 的问题讲述布隆过滤器的原理之前，我们先思考一下，通常你判断某个元素是否存在用的是什么？应该蛮多人回答 HashMap 吧，确实可以将值映射到 HashMap 的 Key，然后可以在 O(1) 的时间复杂度内返回结果，效率奇高。但是 HashMap 的实现也有缺点，例如存储容量占比高，考虑到负载因子的存在，通常空间是不能被用满的，而一旦你的值很多例如上亿的时候，那 HashMap 占据的内存大小就变得很可观了。还比如说你的数据集存储在远程服务器上，本地服务接受输入，而数据集非常大不可能一次性读进内存构建 HashMap 的时候，也会存在问题。布隆过滤器数据结构布隆过滤器是一个 bit 向量或者说 bit 数组，长这样：如果我们要映射一个值到布隆过滤器中，我们需要使用多个不同的哈希函数生成多个哈希值，并对每个生成的哈希值指向的 bit 位置 1，例如针对值 “baidu”

Can't load AMD 64-bit .dll on a IA 32-bit platform 问题

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解决办法：下载一个32位的tcnative-1.dll替换tomcat原先的即可。 0-Dec-2019 09:14:57.113 警告 [main] org.apache.catalina.core.AprLifecycleListener.init 基于APR的本地库加载失败. 错误报告为[D:\java\tomcat\apache-tomcat-9.0.27\bin\tcnative-1.dll: Can't load AMD 64-bit .dll on a IA 32-bit platform]java.lang.UnsatisfiedLinkError: D:\java\tomcat\apache-tomcat-9.0.27\bin\tcnative-1.dll: Can't load AMD 64-bit .dll on a IA 32-bit platformat java.lang.ClassLoader$NativeLibrary.load(Native Method) …………………………………… 下载地址： http://www.apache.org/dist/tomcat/tomcat-connectors/native/ (我下载的是tomcat-native-1.2.21-openssl-1.1.1a-win32-bin.zip，问题解决了！)

Navicat Premium 64 bit 12.1.25

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Navicat Premium可让你以单一程序同時连接到 MySQL、MariaDB、SQL Server、SQLite、Oracle 和 PostgreSQL 数据库，是一个可多重连接的数据库管理工具，它让管理不同类型的数据库更加方便。官方下载地址： https://www.navicat.com.cn/download/navicat-for-mysql 软件特色 Navicat 的功能足以符合专业开发人员的所有需求，但是对数据库服务器的新手来说又相当容易学习。它可让你以单一程序同時连接到目前世面上所有版本的主流数据库并进行管理和操作，支持的数据库有： MySQL、SQL Server、SQLite、Oracle 及 PostgreSQL。让管理不同类型的数据库更加方便。支持Microsoft Windows XP SP2, Vista, Windows 7, Windows 8, Server 2003, Server 2008, Server 2012操作系统！ Navicat Premium 使你能简单并快速地在各种数据库系统间传输数据，或传输一份指定 SQL 格式及编码的纯文本文件。不同数据库的批处理作业可以计划并在指定的时间运行。其他功能包括导入向导、导出向导、查询创建工具、报表创建工具、数据同步、备份、工作计划及更多。 Navicat Premium 结合了其他

BMP文件格式学习总结

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一个BMP文件可以包含4部分 1，文件头是14字节长的数据结构，定义如下： typedef struct _BFHEADER { unsigned short magic; unsigned int size; unsigned int reserved; unsigned int bitOffset; }bfHeader; 2.bmp 信息结构，结构定义如下： typedef struct _bmpInfoHead { unsigned int headSize; unsigned int width; unsigned int height; unsigned short planes; unsigned short bpp; unsigned int compress; unsigned int imageSize; unsigned int PelsPerMeterX; unsigned int PelsPerMeterY; unsigned int ClrUsed; unsigned int ClrImportant; unsigned int RedMask; unsigned int GreenMask; unsigned int BlueMask; unsigned int AlphaMask; unsigned int CsType; unsigned int

C++: Bitwise AND

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问题 I am trying to understand how to use Bitwise AND to extract the values of individual bytes. What I have is a 4-byte array and am casting the last 2 bytes into a single 2 byte value. Then I am trying to extract the original single byte values from that 2 byte value. See the attachment for a screen shot of my code and values. The problem I am having is I am not able to get the value of the last byte in the 2 byte value. How would I go about doing this with Bitwise AND? Thanks for your help,

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