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Questions tagged [bitwise]

For challenges involving doing something on the bit level.

13
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28answers
4k views

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 ...
25
votes
15answers
2k 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 ...
20
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22answers
3k views

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 ...
3
votes
2answers
312 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, ...
15
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17answers
2k views

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 ...
12
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22answers
1k views

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 ...
19
votes
2answers
358 views

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 ...
32
votes
33answers
4k views

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 ...
5
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1answer
228 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 ...
14
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8answers
2k views

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 ...
7
votes
28answers
2k views

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 ...
21
votes
15answers
1k 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 ...
18
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9answers
567 views

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 ...
26
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26answers
2k views

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 ...
14
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4answers
637 views

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 <...
11
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9answers
855 views

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 ...
36
votes
25answers
3k views

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 multiplication ...
42
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29answers
3k views

Bitflip and negate

Given an integer, make an expression that produces it from 0 using unary negation - and bitwise complement ...
14
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21answers
2k views

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 ...
27
votes
26answers
2k views

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 2n items, zero-...
19
votes
12answers
2k views

“Bit-borrow” two numbers

Did you know that a small number can borrow bits from a larger number? Here's an example. Let's say our two numbers 5 and 14. First, write them out in binary: ...
30
votes
42answers
3k views

Mean bits: an average challenge

Given an integer N >= 1, output the mean number of bits in an integer from 0 to N - 1 Specification The output can be calculated as the sum of the number of bits in the binary representation of each ...
14
votes
9answers
1k views

Compute CRC32 Hash

Credits This challenge originated from @miles. Create a function that computes the CRC32 hash of an input string. The input will be an ASCII string of any length. The output will be the CRC32 hash ...
18
votes
23answers
3k views

Generate a parity bit

A parity bit, is one of the simplest forms of a checksum. First, you have to pick the parity, even or odd. Let's say we pick even. Now, we need a message to transmit. Let's say our message is "Foo". ...
22
votes
23answers
4k views

Split a byte array into a bit array

Write a function that when given a buffer b (1 - 104857600 bytes long) and a number of bits n (1 <= n <= 64), splits the ...
22
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10answers
2k views

The XOROR sequence

Cellular Automata are truly fascinating. The ones that are usually talked about are the binary ones, i.e., the ones representable by a number. However, those, in my opinion, have been done to death. ...
4
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2answers
239 views

Bit Manipulator/Reader

Introduction There are often times that we have challenges which require communication of some sort (such as in team KOTH), where density of information may be more important than density of code. ...
11
votes
8answers
519 views

Bijective mapping from integers to a variable number of bits

A variable number of bits is an array of 0 or more bits. So [0, 1] is a variable number of bits, but so is []. Write a function ...
41
votes
34answers
11k views

Cheating a multiple choice test

Introduction While studying, I tried to come up with several ways to cheat a multiple choice test. It basically is a compressed version of the multiple choice answers. The method goes as following: ...
100
votes
17answers
4k views

Xorting an array

Conceptually, this challenge is really simple. You're given a list of non-negative integers ai. If possible, find a non-negative integer ...
19
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21answers
2k views

Produce an XOR table

Introduction XOR is a digital logic gate that implements an exclusive or. Most of the times, this is shown as ^. The four possible outcomes in binary: ...
12
votes
6answers
389 views

Mask an IP address and give its broadcast

Background Inspired by this Unix.SE question (and of course my own answer). When an IP address is specified for an interface, it is often given in this dotted-decimal form: ...
23
votes
25answers
2k views

Compute the Binary Sierpinski Triangle Sequence

The Binary Sierpinski Triangle sequence is the sequence of numbers whose binary representations give the rows of the Binary Sierpinski Triangle, which is given by starting with a 1 in an infinite row ...
16
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5answers
1k views

Find the XOR Primes

In this challenge posed by xnor, we were asked to implement XOR multiplication. In this challenge the goal is to find the first n XOR primes. XOR primes are very ...
0
votes
0answers
61 views

Check if a given 8-bit Number is sparse [duplicate]

The task is the following: Program the shortest fully functional program that checks, if an 8-bit value contains a consecutive sequence of 2 or more ones in its binary form. If it does contain such ...
40
votes
31answers
5k views

Programming with Bits and Bytes

In this challenge you are going to write an interpreter for a simple language I've made up. The language is based on a single accumulator A, which is exactly one byte in length. At the start of a ...
9
votes
3answers
521 views

Summation under Zeckendorf Representation

Zeckendorf's theorem shows that every positive integer can be uniquely represented as a sum of non-adjacent Fibonacci numbers. In this challenge, you have to compute the sum of two numbers in ...
33
votes
22answers
6k views

XOR multiplication

You goal is to implement the operation of XOR (carryless) multiplication, defined below, in as few bytes as possible. If we think of bitwise XOR (^) as binary ...
15
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4answers
846 views

Shifty XORyption

Write a program or function (or set of programs/functions) to encrypt and decrypt data given the following specification: Encryption Calculate an XOR hash of the input by XOR-ing every byte with ...
16
votes
5answers
635 views

Unwise bit operations

I like to golf in dc, but I'm sometimes frustrated because dc doesn't have bitwise operations. Challenge Provide four named ...
27
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19answers
3k views

Vampire Compatibility

A little known fact about vampires is that they must drink the blood of victim that has a compatible donor blood type. The compatibility matrix for vampires is the same as the regular red blood cell ...
10
votes
11answers
1k views

Write a program that turns every 17th bit of a text file to a 1

My coworker and I work on a legacy piece of software that we hate sometimes. Whenever you run it, debug asserts come flying everywhere, and it's never a guarantee that anything will work. The ...
7
votes
8answers
1k views

Extraction of Bits

Your task is to devise a programme that extracts the bits, in order, represented by the first argument based on the set bits represented by the second argument (the mask). Formal Definition: Let ...
13
votes
6answers
3k views

Implement an 8 bit adder

The Challenge Implement a function which accepts two integers whose values range from 0 - 255 and returns the sum of those integers mod 256. You may only use bitwise negation (~), bitwise or (|), bit ...
7
votes
8answers
680 views

Implement bit-wise matrix multiplication

The MMIX architecture is a fairly simple big-endian RISC design. It has a couple of interesting features, one of them is the MXOR instruction, which is what you ...
21
votes
32answers
6k views

Reverse Bit Order of 32-bit Integers

Write the shortest code to reverse the bit order of a 32-bit integer. Rules: Input is assumed to be a valid integer or string equivalent if your language doesn't support numerical values (e.g. ...
5
votes
1answer
313 views

Recover a bzip2 file

The popular .bz2 compression format is used to store all sorts of things. One of the more interesting features is that it consists of several independently ...
35
votes
69answers
13k views

Sort numbers by binary 1's count

Goal Write a function or program sort an array of integers in descending order by the number of 1's present in their binary representation. No secondary sort condition is necessary. Example sorted ...
6
votes
9answers
1k views

Arbitrarily Shift Bit Array Represented As Array of 32-bit Integers [closed]

Given an array of 32-bit integers which represent a bit array, shift the values by a specified amount in either direction. Positive shifts go to the left and negative values go to the right. This is a ...