Questions tagged [bitwise]
For challenges involving bitwise commands or manipulation of numbers at the bit level
79 questions
11
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On the Subject of Switches
This challenge is from a video game, Keep Talking And Nobody Explodes.
A yes or no choice isn’t too bad. Unfortunately you have to make five of them and any of them could be your last. — from the ...
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8
votes
7
answers
944
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Conversion between CESU-8 and UTF-8 (for supplementary characters)
The Compatibility Encoding Scheme for UTF-16: 8-Bit, also known as CESU-8, is a Unicode encoding that is not part of the Unicode standard, but mentioned in a Unicode Technical Report as a ...
- 607
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17
answers
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Find the Smallest Data Type for a Number
Recently I had to implement this problem in c#, and thought it would make for a good code golf.
Your goal is to output the smallest unsigned data-type a 64 bit unsigned number can fit into.
Input: An ...
- 381
5
votes
9
answers
360
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Reorder a string of length \$2^n\$ by permuting the \$n\$ binary digits of every index
Given a binary string \$s\$ of length \$2^n\$ and a permutation \$\sigma\$ of \$\{1,\dots,n\}\$, generate the binary string \$u\$ of length \$2^n\$ which is a reordering of \$s\$ such that \$u[i^\...
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Fast leap year check
The task is to find parameters that make a fast leap year check correct for the widest range of years.
We assume the Proleptic Gregorian calendar, which extends the Gregorian calendar backward from ...
- 491
18
votes
12
answers
2k
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Is it a valid ARM immediate value?
Exposition
In this challenge, I am talking about ARM assembly language. ARM is a 32-bit RISC processor; I'll use instruction set up to architecture v6.
To load a constant ("immediate") value ...
- 14.1k
17
votes
18
answers
2k
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XOR of independent Bernoulli variables
In probability theory, a Bernoulli variable is a random variable which has a single parameter \$p\$, and is equal to 1 with probability \$p\$, and 0 with probability \$1-p\$.
In this challenge, there ...
- 10.9k
2
votes
0
answers
272
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making a binary string palindrome using xor operations [closed]
Problem
You are given a binary string A of length N.
You can perform the following type of operation on the string A:
Choose two different indices \$i\$ and \$j\$ (\$1 \le i\$, \$j \le N\$)
Change \$...
- 21
15
votes
3
answers
621
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Count the number of disjoint 11 blocks
The task is to count the number of disjoint 11 blocks in a 64-bit word, using the minimum number of straight-line instructions. That is, how many nonoverlapping ...
- 491
2
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3
answers
346
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Shift distance of number [closed]
Given two non-zero 16-bit integers a and b, decide the smallest number of shift operations needed to turn ...
- 32.4k
9
votes
3
answers
537
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Smallest and largest 100-bit square with maximum Hamming weight
Introduction
In the binary representation of a \$k-\$bit \$(k>1)\$ square number \$n^2, \$ not all bits can be \$1\$. The maximum number of \$1\$-bits (Hamming weight, \$B\$ for short) is given in ...
- 711
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votes
2
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691
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Inverting string-based binary number in one line in Python
I want to read two strings on separate lines, each string the same length and containing only 0's and 1's, and determine if the first is the one's complement of the second. How succinctly can this be ...
- 191
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votes
19
answers
713
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Double bit rotation to the right [closed]
Given a positive integer as input, output that integer, but with its bits rotated two times to the right. Also, think of the number as a donut of bits, eg. ...
- 2,080
0
votes
4
answers
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Calculate the truncated log2 of some unsigned integer [duplicate]
Definition
Given some number, x calculate the smallest number i such that 2i≥x. This is not a duplicate of this question. It is slightly different in that an input of 16 should yield an output of 4 ...
- 357
6
votes
3
answers
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Dr. Lamport's Unfinished Business
Introduction
Dr. Leslie Lamport, of the eponymous Lamport one-time signature scheme, is getting rather old. But he can't die until his most famous algorithm gets all the kinks ironed out!
In ...
16
votes
6
answers
968
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Golf this Thumb-2 Constant!
One thing that is constantly frustrating when golfing ARM Thumb-2 code is generating constants.
Since Thumb only has 16-bit and 32-bit instructions, it is impossible to encode every immediate 32-bit ...
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18
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9
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The Koszul Sign Rule
A Bit of Background
The exterior algebra is a central object in topology and physics (for the physics concept cf. fermion). The basic rule dictating the behavior of the exterior algebra is that \$yx =...
- 2,115
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votes
9
answers
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Simulate D Flip-Flop
Objective
Simulate an edge-triggered D Flip-Flop.
What is D Flip-Flop?
A D flip-flop is an electronic digital device that outputs an inputted data (abbr. D) with synchronization to a clock (abbr. ...
- 7,371
16
votes
23
answers
2k
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Summing a sub-square of a quarter of an infinite chessboard
Description of the problem
Imagine a quarter of an infinite chessboard, as in a square grid, extending up and right, so that you can see the lower left corner. Place a 0 in there. Now for every other ...
- 14.2k
7
votes
13
answers
315
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Computational Parity Party! [duplicate]
The computational parity of an integer is defined as 1 if the integer has an odd number of set bits, and 0 otherwise. (src).
Input
You will receive one nonnegative integer that you will take the ...
- 3,358
29
votes
12
answers
4k
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Compress 8 bits to 6 when certain bit patterns will never occur
Consider an eight bit number in which an even position (second, fourth, etc) bit will never be 1 if one of its neighbors is 0 (considering MSB and LSB as neighbors). There are fewer than 64 such ...
- 6,136
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votes
7
answers
512
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Interpreting the Wolfram Code
Introduction
An elementary cellular automaton is a cellular automaton that is 1-dimensional and has 2 states, 1 and 0. These cellular automata are categorized based on a simple code: the Wolfram code,...
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votes
2
answers
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Mirror, Mirror, on the wall. Who's the fairest of them all?
Well, you know it's Snow White, and the evil Queen is at it again. Will Snow White be saved? Will she fall asleep once again? Will the Prince find her?
Challenge:
Given an arbitrary number (>= 2) ...
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votes
22
answers
9k
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Floating Point XOR
Your task is pretty simple. Given two floats, bitwise xor the binary representation of them, and output that as a float.
For example,
...
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votes
22
answers
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Decode a variable-length quantity
A variable-length quantity (also referred to as VLQ or uintvar) is a way to encode up to a 28 bit integer value using only as many bytes as necessary. This was used ...
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votes
30
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String to Bit Transition
Task
Given an input string of one or more ASCII characters which codepoints are between 0 and 128 (exclusive), do the following:
Convert each character into its 7-bit ASCII code (if the ASCII code is ...
- 2,279
19
votes
22
answers
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I'm in your subnets, golfing your code
Challenge
Given an IPv4 address in dotted-quad notation, and an IPv4 subnet in CIDR notation, determine if the ...
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31
votes
2
answers
1k
views
Can a neural network recognize primes?
Background
Recognizing primality seems like a poor fit for (artificial) neural networks. However, the universal approximation theorem states that neural networks can approximate any continuous ...
- 2,617
10
votes
21
answers
2k
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Compare four integers, return word based on maximum
This function should take four integer inputs (a,b,c,d) ...
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vote
1
answer
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(bit)Wise Images [closed]
Given a truth table and two images, use the truth table as a bitwise operation to the two images.
For example with the truth table:
1 0
1 0 0
0 1 0
(Note that ...
- 2,742
19
votes
32
answers
9k
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Find the number of leading zeroes in a 64-bit integer
Problem:
Find the number of leading zeroes in a 64-bit signed integer
Rules:
The input cannot be treated as string; it can be anything where math and bitwise operations drive the algorithm
The ...
- 335
26
votes
17
answers
3k
views
Toggle some bits and get a square
Given an integer \$N>3\$, you have to find the minimum number of bits that need to be inverted in \$N\$ to turn it into a square number. You are only allowed to invert bits below the most ...
- 206k
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22
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Double, XOR and do it again
We define the function g as g(n) = n XOR (n * 2) for any integer n > 0.
Given x > 0, find the smallest integer y > 0 such that gk(y) = x for some k > 0.
Example
...
- 206k
3
votes
2
answers
395
views
Wanna be an Alchemist
Wanna be an Alchemist
I've been watching Full Metal Alchemist these past days and I've been wondering, It is really possible to trans-mutate matter? In the real world, I don't know if it is possible, ...
17
votes
17
answers
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XOR sort an array
Given a key, and an array of strings, shuffle the array so that it is sorted when each element is XOR'd with the key.
XOR'ing two strings
To XOR a string by a key, XOR each of the character values ...
- 11.7k
13
votes
23
answers
2k
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Alternating bit smearing
Introduction
This challenge requires you to set the trailing zeros of an integers binary representation to 010101…, this is best explained with an example:
Given ...
- 17k
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votes
2
answers
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Bitwise XOR of rational numbers
Introduction
Every rational number between 0 and 1 can be represented as an eventually periodic sequence of bits.
For example, the binary representation of 11/40 is
...
- 43.2k
34
votes
36
answers
6k
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Calculate the longest series of 1's in an integer's binary value
Goal
Given a non-negative integer, create a function that returns the starting position of number of largest consecutive 1's in that integer's binary value.
When given an input ...
- 575
4
votes
1
answer
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views
Find the Closest Double Palindrome
Given a double-precision float, find the closest double-precision float whose binary representation is a palindrome.
Input
A floating point number x. You may use ...
- 2,898
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8
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Exploring the xorspace
The xorspace of a set of integers is the set of all integers that can be obtained by combining the starting integers with the usual bitwise xor operator (^). For ...
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10
votes
32
answers
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Do two numbers contain unique powers of 2
Break two numbers up into their powers of 2, if they share any, return a falsey value. Otherwise, return a truthy value.
If one input is 0, the answer will always ...
- 11.7k
22
votes
19
answers
2k
views
Different number, same weight
Background
The Hamming weight of an integer is the number of ones in its binary representation. For this challenge, integers are represented with 32 bits, and they are unsigned.
Challenge
Given an ...
- 4,802
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votes
9
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726
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Make Wise Numbers
Wise is a simple bitwise language I designed a while back. It is based around Python's bitwise operations. It has several operations most of these are the same or very similar to the equivalent ...
- 103k
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26
answers
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Digital Hardness of Integers
To find the digital hardness of an integer, take its binary representation, and count the number of times both a leading and trailing 1 can be removed until it ...
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17
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5
answers
2k
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Binary Convolution
A binary convolution is described by a number M, and is applied to a number N. For each bit in the binary representation of <...
user45941
10
votes
9
answers
1k
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Super Folding Numbers
We have already defined a folding number here.
But now we are going to define a Super Folding Number. A Super Folding number is a number that if folded enough times it will eventually reach one less ...
- 103k
38
votes
27
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Folding Numbers
Given a number determine if it is a folding number.
A folding number is a number such that if you take it binary representation and "fold" it in half, That is take the result of XNOR ...
- 103k
42
votes
29
answers
3k
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Bitflip and negate
Given an integer, make an expression that produces it from 0 using unary negation - and bitwise complement ...
- 150k
14
votes
22
answers
3k
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Golf bit weaving
Note: the first half of this challenge comes from Martin Ender's previous challenge, Visualize Bit Weaving.
The esoteric programming language evil has an interesting operation on byte values which it ...
- 50.6k
29
votes
30
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Bit-Reversal Permutations
Your goal is to create a function or a program to reverse the bits in a range of integers given an integer \$n\$. In other words, you want to find the bit-reversal permutation of a range of \$2^n\$ ...
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