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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67 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
51 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
92 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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votes
1answer
148 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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0answers
48 views
FUTABA SBUS serial communication in C++
I would like to reimplement the current Futaba SBUS protocol in ArduPilot for Navio+. It seems to be a relatively expensive protocol, so I changed the code from an existing git project and to make it ...
3
votes
1answer
31 views
Routine for 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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votes
5answers
73 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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votes
2answers
154 views
Java conversion of base 16 to base 64
I wrote a solution in Java to solve the problem here. I use BigInteger to convert first from base 16 to base 10, then base 10 to base 64.
This seems quite ...
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1answer
88 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
58 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 ...
7
votes
2answers
114 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
votes
1answer
50 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 ...
3
votes
1answer
33 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 ...
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votes
1answer
61 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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votes
2answers
77 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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votes
3answers
260 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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votes
0answers
90 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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vote
1answer
81 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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vote
1answer
62 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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votes
1answer
80 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 ...
3
votes
1answer
67 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
83 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
112 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 ...
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votes
2answers
589 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
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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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votes
3answers
336 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 ...
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3answers
311 views
Mockup in C of hardware implementation for multiplication of signed integers
I challenged myself to implement multiplication of signed integers using only +, -, ...
3
votes
1answer
65 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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vote
1answer
207 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
188 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 ...
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votes
1answer
135 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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votes
3answers
109 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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votes
3answers
142 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
...
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votes
2answers
224 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
votes
2answers
184 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 ...
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votes
2answers
92 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 ...
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1answer
75 views
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1answer
474 views
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2answers
346 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
votes
1answer
217 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
2k 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 ...
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votes
1answer
418 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 ...
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votes
1answer
503 views
An Army of Ones
I've been practicing using recursion lately and thought this was a case where it would prove really useful, is this good use or is there some superior non-recursive way to go about it?
Challenge:
...
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votes
1answer
489 views
Bitwise operators for permissions
I'm trying to create a read-write-execute permissions system for items using user-group-world system.
I already have the user/group system set up, just not the permissions.
This is what I wrote:
...
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votes
1answer
1k views
XOR of a list of a numbers
In preparing a solution for the CodeChef "Will India Win" challenge, I am trying to find out the xor of list of numbers.
The first line of input contains the number of test cases, 1 ≤ T ≤ 106.
...
4
votes
1answer
158 views
Copy arbitrary number of bits at arbitrary offset from buffer to another buffer
I have just written a function copy_lowbits_off to copy any number of bits (not bytes) from a source buffer to a destination buffer. The function also supports ...
0
votes
1answer
90 views
Portable bitfields code generator
I am working on a project that involves quite a lot of instantiated objects, with tons of properties, most of which have only a few possible values, so the prospect of saving on memory is quite ...
4
votes
5answers
3k views
Reversed Binary Numbers
Here is my code for "Reverse Binary Numbers" in C.
Problem
Your task will be to write a program for reversing numbers in binary.
For instance, the binary representation of 13 is 1101, and ...
7
votes
7answers
904 views
Changing element visibility based on multiple checkbox states
I am writing a script in JavaScript & HTML and have some optimization problems. In the for, loop I check a variable named ...
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votes
0answers
29 views
Bit stream input in Factor
My attempt at writing code to input values of arbitrary bitlength based on a bytearray in Factor. Any comments on the correctness or style would be appreciated.
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