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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127 views

A bitwise common prefix algorithm in Python

Is my algorithm slow because it has problems? Or, is any bitwise common prefix solution not going to give me the performance I'm looking for? After profiling my algorithm, I found that over 60% of ...
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1answer
270 views

Console app to teach bitwise operators

I'm creating a console app that has the purpose to teach you how to use C# bitwise operators. I have several classes which contain info about the different operators and I instantiate/add them in the ...
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1answer
371 views

Parsing an IP address (Bit manipulation)

Given a string representing of an IP address, such as "127.43.23.59", return a 32 bit integer representation of this string. The 32 bit integer is separated into four bytes, where each byte is one of ...
8
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1answer
316 views

Calculating the results of bit operations

I have a simple program that calculates and outputs the results of all the bit operators. I'm planning to send it to my friend and to explain some stuff about them to him. Before I do that, I want to ...
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2answers
8k views

Printing longest sequence of zeroes

I am doing a coding exercise in codility and I came across this question: A binary gap within a positive integer N is any maximal sequence of consecutive zeros that is surrounded by ones at both ...
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2answers
960 views

Concatenate three 16-bit integers in one 64-bit integer with C++

I am looking for an elegant alternative of the following code where wordXX contains always 16 bits: ...
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2answers
1k views

Portable byte order conversion

I'm trying to improve the portability of a file format converter, specifically to POSIX platforms other than Linux. I'd appreciate a review of the following functions used for converting between ...
4
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0answers
126 views

Parallel popcount of packed bytes

I want to do a popcount of bytes in an array. Not a total popcount of everything, but lots of little popcounts for every individual byte to determine the neighborhood count in GoL. The following ...
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2answers
1k views

BMP writer in C

I recently wrote a BMP writer in C: bmpWriter.h ...
3
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3answers
493 views

Bit manipulation tool set

I made a tool set to facilitate bit manipulation as follows. Any comments are welcome, be it about the interface design, the implementation, or even the naming. Also, I want to make sure that the tool ...
5
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1answer
170 views

Speeding up the generation all bit strings with Hamming distance one

I'm playing around with hypercubes. For this, I need to create its edge set. Specifically, the edge set is the set of all bit strings with Hamming distance 1. An important property is that I want to ...
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1answer
2k views

Saturated signed addition

So this a exercise from the book COMPUTERS SYSTEMS A PROGRAMMERS PERSPECTIVE I need to add two signed numbers and in case it overflows or underflows return ...
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2answers
203 views

Simulation of image transfer over noisy channel

Following this question, I've tried to rewrite some core methods to avoid using String for bit operations, and I ended up using ...
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1answer
219 views

Solution to part 1 of Day 7 Advent of Code in Scala

Does someone want to review my solution to part 1 of Day 7 Advent of Code in Scala? The assignment is here: http://adventofcode.com/day/7 Without repeating the whole text, in short: Given a text file ...
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1answer
140 views

Routine to convert decimal digits to Densely Packed Decimal

I've written an amd64 assembly routine (in gas syntax using the System V calling convention) to convert three decimal digits to Densely packed decimal because I wasn't satisfied by the performance of ...
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5answers
134 views

Toggle four relays on/off based on bitmap stored in uint8_t

I am using a one-byte bitmap to control four relays. I am writing a function which will take the bitmap stored as uint8_t, look to see which bits are set/cleared, ...
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1answer
4k views

Remove elements existing in a list built from an enum

The objective of this code is to make the difference inbetween two lists of items, that is knowing which items are missing in the second list in regards to the first one. The first list is built from ...
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3answers
162 views

Testing if the binary representation of an integer has an odd number of ones

The fn odd_ones(x: u32) -> bool function should return true when x contains a odd number ...
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2answers
191 views

All arithmetic operator functions (+, -, *, /, %) coded only using bitwise operators in C

Here's all the functions in C that does all the arithmetic operators without using arithmetic operators themselves, mostly using bitwise operators. Recursive functions and comparison operators are ...
2
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1answer
64 views

Three ways to read a number for a BitInputStream

I'm trying to learn how to write more readable code without introducing easily avoidable performance killers. This is part of a BitInputStream Java class I'm ...
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1answer
45 views

PWM wave generation

This code takes a integer x of range [0,127] as input, returns an array of four 32-bit integers, with x bits set. I'm trying to ...
3
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1answer
75 views

Testing for divisibility of numbers - follow-up

(Here is the follow up question) I had another go at trying to speed up my program described in my previous question. JS1's answer was particulary helpful and now my code is only about 20% slower ...
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2answers
107 views

Program to test for divisibility of numbers

(EDIT: here is the follow up qusetion) Using this program to test for the smallest number where its permutations or itself is divisible by 10 or less numbers is twice as slow as the fastest program I ...
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3answers
1k views

Finding nearest power of 2

I have the following simple program which calculates and returns the nearest power of 2 of a given number. Because I use increments and decrements to find the closest power, this takes a very long ...
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0answers
898 views

Read bits, write bits data to arbitrary position in char array

I created functions to read bit data from arbitrary bit position of a char array to long long int, and I also created a function ...
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1answer
2k views

Bitmask type to perform binary operations

Without any specific implementation details, how would you create a bitmask type that wraps binary arithmetic into something easy to read? Ideally, this would be used with an ...
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1answer
4k views

“Flipping bits” Python implementation

Problem Statement You will be given a list of 32 bits unsigned integers. You are required to output the list of the unsigned integers you get by flipping bits in its binary representation (i.e. ...
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1answer
155 views

Return Y integer with same bit sets as X & having | X - Y | minimum value

I happened to come across one question: Given an integer 'x' (Only positive), write an algorithm that returns integer 'y' such that it has the same number of bits set as 'x' and is not equal to ...
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1answer
107 views

Code Chef problem COOKMACH

Firstly, I got the solution for this question in CodeChef, but I noticed one thing which still confuses me. This was the code which was accepted as correct. ...
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1answer
2k views

Reading bits from a stream from least to most significant

For a recent project I was in need of excessive bit manipulation. Specifically, I had to write to or read from a variable number of bits up from the least significant bit towards the most significant ...
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3answers
168 views

Performing add/delete/count operations on a list

Problem Statement (HackerRank) You have a list of integers, initially the list is empty. You have to process Q operations of three kinds: add s: Add integer s to your list, note that ...
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2answers
653 views

Division without multiplication, addition or division

In context of preparing for a coding interview, I gave the division problem a go using Java. This is what I came up with. It's a little bit different to other solutions I've come across the interweb. ...
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8answers
4k views

String reversal, capitalize vowels, lowercase consonants

This was a portion of a skills test given to me by a company. The task was to write a method that takes a string, reverses it, and sets the vowels as capitals and consonants to lowercase. I was also ...
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3answers
3k views

Number of right cyclic shifts to give the biggest number

I am preparing to coding interview and I met this task today: You are given 30-bit unsigned integer N. A right cyclic shift of N by K bits is the result of performing a right cyclic shift of N by one ...
3
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3answers
368 views

Mockup in C of hardware implementation for multiplication of signed integers

I challenged myself to implement multiplication of signed integers using only +, -, >>,...
3
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1answer
426 views

Encoding variable-length quanties for MIDI

I was reading about the MIDI spec and I challenged myself to implement a function to convert an int32 to a variable length quantity uint32. I didn't look it up or ...
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1answer
1k views

Pixel bit-wise LSB extraction to byte array

I wrote the following code below to extract the least significant bit (LSB) of each pixel and store it into a byte[] array. I was wondering if Java has a more ...
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2answers
704 views

Verifying validity of Intel.hex file records

I have a class called FirmwareFile which represents and Intel HEX format file. The file is constructed with the name, build time and build date, at a later point ...
5
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1answer
152 views

Printing lines in a file, filtering by the first column

I am setting up a project which involves a lot of data analysis, each data point represented by a line in a large text file. In order to test for certain types of data, I added a tag to each line (It ...
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3answers
644 views

Bitstream reader

I have a program which reads and analyses MPEG-TS files. I've been using gperftools to identify hotspots and optimize them, and 45% of all samples at this point are in my main bitstream reader ...
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3answers
350 views

Fastest sum of absolute values of 32 differences

A long should be treated as a list of 32 unsigned numbers, each of them just two bit long. So 0x1234F... represents ...
9
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2answers
626 views

Gray codes addition — Take 2

For a while, I have tried to find ways (known or new) to do stuff with Gray codes. As some of you probably know, I already tried to implement an algorithm to add two Gray codes without having to ...
2
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2answers
968 views

Simple Binary Adder

The program adds two binary numbers in two' s complement ignoring the overflow for a constant size of bits. I am trying to generalize the program by taking input from the user in a single line without ...
3
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2answers
156 views

Given bit strings, perform a bitwise addition

I'm looking for code-review, optimizations and best practices. This code is a Java adaptation of code on geeksforgeeks.org. Please verify if space complexity is \$O(n)\$ where n is number of bits, and ...
2
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1answer
109 views

Pseudo-random number generator port from C

C code: ...
3
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1answer
6k views

Byte-to-binary conversion function

My implementation of a binary-to-bits converting function: ...
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2answers
1k views

Calculating holes on a Tetris grid quickly

I have created a Tetris AI which can play Tetris on its own given a set of rules. It places the next piece in every possible way on the board, and calculates which position that gives the fewest "...
3
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1answer
1k views

Network byte order to host byte order

While doing a little project involving sniffing packets, I found myself programming a cross platform network to host byte order and host to network byte order, this is my first time developing a ...
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2answers
11k views

Packing and unpacking two 32-bit integers into an unsigned 64-bit integer

Does this look good for combining/retrieving two 32 bit integers (a type and an index) into/from an unsigned 64 bit integer (a unique ID)? The point is to hide in the API the composition of the ...
4
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1answer
1k views

Optimizing code to find maximum XOR in Java

This problem is from HackerRank (not a competition, just for practice) Basically what you do is take in two integers as a range and then finding the maximum XOR from a pair of integers in that ...