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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40 views
Fast constant time evaluation of “x==7” to 1 (true) or 0 (false) in Java [migrated]
I want to port a crypto function from C to Java. The function has to run in constant time, so no conditional branchings are allowed.
The original C code is:
...
6
votes
1answer
44 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 ...
2
votes
0answers
34 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
46 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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4answers
106 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 ...
4
votes
2answers
543 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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5
votes
8answers
677 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 ...
3
votes
3answers
161 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
292 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
47 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
112 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 ...
5
votes
2answers
85 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 ...
4
votes
1answer
130 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 ...
4
votes
3answers
83 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 ...
10
votes
3answers
133 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
...
8
votes
2answers
185 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
171 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
votes
2answers
82 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
69 views
2
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1answer
199 views
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2answers
260 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
96 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 ...
10
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2answers
880 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
votes
1answer
253 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 ...
7
votes
1answer
500 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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4
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1answer
276 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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2
votes
1answer
556 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.
...
3
votes
1answer
99 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
78 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
2k 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
741 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 ...
3
votes
0answers
25 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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7
votes
2answers
114 views
Speed optimization for transparent gradient blend algorithm
The following algorithm works correctly for the purposes that I need, which is to set the top side of an image with a transparent gradient blend. Any tips to optimize it for speed?
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4
votes
2answers
1k views
Binary to decimal number converter
Here I am doing some exercises for my studies with Python. This is a binary to decimal number converter (currently restricted to that).
These are the very first steps, so there is no error handling. ...
2
votes
2answers
226 views
Computing pairwise bitwise OR in a list of bit-strings
I am trying to solve this problem using Clojure:
You are given a list of \$N\$ people who are attending ACM-ICPC World
Finals. Each of them are either well versed in a topic or they are
not. ...
17
votes
2answers
479 views
Gray codes addition
As some of you know, I have been working with Gray codes and am trying to design a good gray_code class in modern C++. I will end up posting several parts of the ...
3
votes
1answer
119 views
Implementing binary output to a file in C++11
I would like to have a class which supports outputting bits into a file. This is what I came up with but I fear there are many poor decisions. Should I inherit from a ...
10
votes
2answers
215 views
Embedded C# bitpacked arrays to low-level STM32F4 driver for GE G35 RGB LED Christmas tree light
I'm going to be opensourcing some code I'm working on. I don't need help with the code, I just want to make sure my code is readable and my comments make sense. I have a knack for the esoteric. ...
9
votes
1answer
425 views
Mostly portable 128 by 64 bit division
I wrote this out of curiosity. It is based on the theory behind Knuth's Algorithm D and is intended to emulate the behavior of the x86 div instruction (though the ...
8
votes
1answer
157 views
Saving bytes instead of objects to write smaller files
This question is about reducing the size of files saved to disk in an infinite world 2D mining game.
I finally added code to my game to save and load distant chunks instead of keeping all of them ...
6
votes
2answers
163 views
Count bits that differ between integers X and Y
I'm trying to solve the following problem :
You are given two integers, X and Y. Calculate the number of bits that will be changed in order to convert integer X to integer Y.
Here is my ...
10
votes
1answer
272 views
Logical shift with signed numbers
I am going through the Coursera course The Hardware/Software Interface and because it has already ended, I would not be able to get any feedback on the code.
The assignment is:
LogicalShift: ...
8
votes
2answers
165 views
Lossy packing 32 bit integer to 16 bit
I am working on the lossy 16 bit representation for 32 bit integers that catches all 32 bit range with precision depending on absolute value.
My idea is to store integer ...
11
votes
1answer
979 views
Steganography for images
For a school project I'm working on a small library to do steganography. I've just finished the first method of steganography and thought I'd get some feedback.
This steganography method works by ...
7
votes
2answers
166 views
Array-like container for uints shorter than 8 bits (Rev 1)
This is a follow-up to Array-like container for uints shorter than 8 bits
In short: The PackedBitfieldArray should be a kind of container for packed (unsigned) ...
11
votes
1answer
152 views
Array-like container for uints shorter than 8 bits
Follow-up: Array-like container for uints shorter than 8 bits (Rev 1)
First of all: yes, I need this kind of array to generate data for a piece of hardware, and it must be stored and manipulated ...
21
votes
3answers
1k views
Diamond in the rough! Finding Gems in the rocks
Recently a question was asked that solved a hackerrank problem: Counting gems amongst the rocks
The description of the challenge is:
John has discovered various rocks. Each rock is composed of ...
5
votes
1answer
128 views
Bitwise operation to get the weekday name
The function days_name receive a val (string) corresponding to weekdays in hexadecimal.
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3
votes
2answers
261 views
Emulating __uint128_t
I developed a lot of code locally with __uint128_t only to find out that it is not available on the target platform.
I am now trying to write my own struct that ...
7
votes
1answer
452 views
Hexadecimal to RGB conversion
I am trying to convert hex to rgb, and rgb to hex. My current code doesn't seem optimal, and there is an issue with 0's in the hexadecimal. What do you think about the overall quality of this code? ...
