Questions tagged [bitwise]

Bitwise refers to a bitwise operation which operates on one or more bit patterns or binary numerals at the level of their individual bits.

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Implementing Generic, General, Specific and Portable Bitwise Operations

First my appologies. My mental faculties currently leave rather a lot to be desired and I have thus spend an inordinary amount of time on this pet project of mine, testing myself if you will. I find ...
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Bit vector in Java supporting O(1) rank() and O(log n) select() - follow-up

(This post is the continuation of Bit vector in Java supporting O(1) rank() and O(log n) select(). It resides here (version 1.0.1).) Basically, I have implemented everything harold suggested, except ...
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Bit vector in Java supporting O(1) rank() and O(log n) select()

Introduction I have this GitHub repository (version 1.0.0.). It implements a rank(i) operation in \$\Theta(1)\$ time, and ...
coderodde's user avatar
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Space efficient arrays

I needed a very space-efficient structure to store an array for which elements are unsigned integers with an upper bound known at runtime. I'm not an expert in pointer arithmetic, so I'm not sure if ...
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C Bit Utility Functions: Popcount, Trailing Zeros Count, Reverse All Bits

Here are some utility bitwise functions for 64 bit integers. I have independently derived inv64 (inverse all bits) and pcnt64 (...
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Convert 64-bit Gray code to integer

This algorithm encodes a 64 bit integer. As input I have a 64 bit integer a, for example: (a is a single 64 bit number,which I split in 8 bytes for readability) <...
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Finding the kth smallest number where all (hexadecimal) digits are different

I'm mostly trying to understand why the simpler char array mask below (to track which digits have been already used) is much ...
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C idiom for multi-layer buffered input with processing

I'm writing a bit-level IO code that handles endianness conversion for the short/uint16_t type in the IO subroutines. Here's the code: ...
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Interleave Bits Generically

This commonly referenced "bit twiddling" site has an interesting algorithm for interleaving the bits of two 32-bit integers. Here is my attempt at completely generalizing the algorithm using ...
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C++ Bitwise adjacency matrix implementation

I have tried to implement a bitwise adjacency matrix to represent a graph with a fixed number of vertices. Instead of wastefully representing each connection with an integer, 64 connections are ...
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Leetcode 137: Single Number II -- python bit operations

I solved LeetCode 137 in C++. TLDR of the problem: array of numbers, nums is given; all numbers appear 3 times, except one which appear only once. Find the number ...
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Access integer field in network packet

I see three complexities in accessing (reading/writing) integer field in network packet. Handle endianness. Integer in network packet is big-endian (BE). The host may be either big-endian or little-...
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Compute the sum of even numbers between two values

Recently I was watching two YouTube videos criticizing a function which sums the even elements in an inclusive range, the original function looks like this: ...
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2 answers
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Less redundant and clearer implementation of action triggers from two modules

(Before I even start: For reasons beyond my control, this code base is constrained to C++98 (so, no =delete, no auto etc., but ...
Peter - Reinstate Monica's user avatar
3 votes
1 answer
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Portable integer to/from little endian conversion in C

Integers need to be converted to a byte array of defined endianness to be reliably and consistently saved and transmitted, and converted back to be accurately received and read. The goal is to be as ...
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SortedIntSet: a set of integers that can be iterated in ascending order in O(N) time

I needed a set with the following properties: can be iterated in ascending or descending order in \$O(N)\$ time the usual set operations (contains, add, remove, discard) can still be done in \$O(1)\$ ...
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Integer multiplication without using multiply operator

I wrote a method that multiplies two integers. Is there a faster approach that doesn't use the * operator? The method mult(a, b) ...
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Electronic circuit logic gates simulator

I've seen a lot of C++ simulators implementing logic gates, but absolutely all of them use the wrapped bitwise operations of the programming language itself. I have tried to omit the use of a bitwise ...
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Counting initial bits of 0 in Java

I want to count the number of bits set to 0 at the beginning of a byte array. So far the code I have is this: ...
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Convert a c# decimal to big-endian byte array

Following the avro schema documentation for decimals I've created a method to turn a decimal into a byte array. The goals are: Should be represented by a non-scaled integer Should be big-endian I've ...
NickL's user avatar
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C++ Chess Engine - (Magic)Bitboard-based move generation

I am currently writing a bitboard-based Chess Engine in C++, and I recently finished the move generation. I am using move-lookup-tables that get pre-calculated at application startup for sliding and ...
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Algorithm to find the sequence of bits that makes up to a given number

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Calculate Hamming distance between integers with bitwise operations

I recently learned about the Hamming distance. The use-case I found it through was actually working with integers instead of strings, yet its implementation was using string comparison. I was pretty ...
Hazel へいぜる's user avatar
1 vote
4 answers
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Permuting BitSet in Java

I have this tool for permuting bits in BitSets: com.stackexchange.codereview.util.BitPermutation.java: ...
coderodde's user avatar
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(Google Foobar XOR Checksum Challenge) How do i optimize this function to run for much larger values?

I wrote a function that accepts 2 integers start and length as input and returns the bitwise XOR of certain numbers as described below: ...
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Converting whole numbers to binary in C/C++

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Separating odd numbers and even numbers into two vectors in C++

I'm learning C++, and would like some guidance. I'm pretty sure I'm doing something wrong. This algorithm runs in O(n) time and uses O(n) external space. Could I make a more efficient algorithm for ...
Asher I's user avatar
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4 votes
1 answer
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LetterDict, a dictionary whose keys must be lowercase letters [a-z]

Looking for any suggestions - alternative design, improvements to readability, improvements to the comments, etc. I implemented this letter dictionary to see if it would faster than a regular ...
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Recursive function that gives the number of hashes present in a Merkle Mountain Range proof

I have written a function that gives the number of hashes present in a Merkle Mountain Range proof. Using Solidity, this function can be written as: ...
Tristan Nemoz's user avatar
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Transformations on a game board represented as a bitset

I'm using a long as a bitset to represent a game board. If a field is set (X) the corresponding bit is set, if it's empty (...
martin's user avatar
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Counting Cram game positions in C

This code counts the number of possible positions in the game of Cram on a mxn board. EDIT 1: In the original question I mistakenly mentioned that this number is ...
martin's user avatar
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UPDATEIT SPOJ problem using Segment tree

UPDATEIT on SPOJ: UPDATEIT - Update the array ! #bitmasks You have an array containing n elements initially all 0. You need to do a number of update operations on it. In each update you specify l, r ...
DRV's user avatar
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Barebones DNS Client in Rust

I'm starting to learn about networking and as a project I am building a really simple DNS client in Rust. Functionality to start was just to take a command line domain argument and sending a DNS A ...
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2 answers
1k views

Representing Tic-Tac-Toe using a binary BitBoard

So I have been learning more about binary numbers lately, particularly in related to describing a gamestate. While perhaps chess is the most natural candidate I wanted to start of with something ...
N3buchadnezzar's user avatar
3 votes
4 answers
97 views

Move an unaligned bit-addressed range into another bitmap

Context I have an array of maximum-fixed-size, size, containers of items; these items are either pointers to objects or an index of the same array, (but no loops.) ...
Neil's user avatar
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2 votes
2 answers
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Generate mask for non zero (or inverse) nibbles in integer

Apologies for the cryptic title, but the problem really is rather simple. I have a 64 bit integer which I interpret as 16 4 bit nibbles, or a nibble array if you wish, and I needed generate a mask ...
Zacariaz's user avatar
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3 answers
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How to refactor a method with many prameters that sets a bit array

I've written a method that is going to set a bit array by passing bool parameters to be able send correct command ...
Mass's user avatar
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Generating Unique Subsets using Bitmasking

Given an array arr[] of integers of size N that might contain duplicates, the task is to find all possible unique subsets. Link to the judge: LINK Note: Each subset should be sorted. Example 1: ...
Shubham Prashar's user avatar
3 votes
1 answer
275 views

Invert n bits beginning at position p of an unsigned integer

In an attempt to create a function that returns x with the n bits that begin at position p ...
j3141592653589793238's user avatar
1 vote
2 answers
253 views

Determine whether bitwise-OR of sub-array is odd

Problem: Given an array A of N integers, you will be asked Q queries. Each query consists of two integers L and R. For each query, find whether bitwise OR of all the array elements between indices L ...
the_illuminated2003's user avatar
4 votes
0 answers
599 views

BitVector64 implementation

I have implemented a structure to handle BitVector64 (default System library support only 32 bits). In the implementation i have added some custom method to manipulate bits inside the vector. I would ...
Skary's user avatar
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4 votes
1 answer
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Generically convert bytes to integers

I wanted to know If there was a way to make it more versatile or shorter/simpler. Here's the code: ...
Guillaume Racicot's user avatar
3 votes
2 answers
933 views

Random alphanumeric string generator function (C, Windows, bcrypt.h)

The function uses the Windows "Cryptography API: Next Generation" (bcrypt.h)'s BCryptGenRandom function to generate ...
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5 votes
1 answer
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Bitarr class optimization C++

I have implemented a bitarr class that does bit manipulations. I would love to know if there is any way to make the code more optimized. Any input would be much appreciated. Thank you! Note: int main()...
starrk's user avatar
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3 votes
2 answers
520 views

Bit manipulator (reader / writer)

Please take a review of my simple bit manipulator: ...
Harry's user avatar
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2 answers
645 views

How to optimize bitwise get/set/clear of ranges of bits on 8-bit integers in JavaScript?

I have been working for a few days on writing get, set, and clear bitwise functions in ...
Lance's user avatar
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3 votes
1 answer
65 views

Array-like data structure for fixed sized types with non-machine-word sizes

I am writing an array-like data structure for types other than 8 16 32 64 – the usual type sizes. Ideally, my interface is the following for addressing the array. ...
honeypot's user avatar
9 votes
1 answer
1k views

Parsing a sequence of bits out of a bit field

For homework, I had to parse CPUID instruction output in C, which required a lot of specific bit-manipulation like: (eax & CACHE_LEVEL) >> 5 I ...
Carcigenicate's user avatar
3 votes
0 answers
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Implementing a Hilbert-like space-filling-curve conversion in Rcpp

I have written a series of functions that are designed to create a space-filling curve (similar to a Hilbert Curve) that is intended for symmetric matrices (as opposed to a square region). I plan to ...
Lewkrr's user avatar
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Factoring the powers of 2 in Python

The powers of 2 are trivial to factor because all powers of 2 have one 1-bit and the rest 0-bits. Just iterate minus one 0-bit as follows: 10000,1000,100,10,1. And then convert the binary strings into ...
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