Questions tagged [number]
This challenge is intended to be solved by using, manipulating, accepting as input, or outputting numeric values.
1,122
questions
10
votes
14answers
308 views
Golf a bijection \$\mathbb{N}^n\to\mathbb{N}\$
Your task is to write a program which implements a bijection \$\mathbb{N}^n\to\mathbb{N}\$ for \$n \ge 1\$. Your program should take \$n\$ natural numbers as input, in any acceptable method (including ...
21
votes
8answers
1k views
Count the Collatz survivors mod 2^n
Introduction
We have 22 Collatz conjecture-related challenges as of October 2020, but none of which cares about the restrictions on counter-examples, if any exists, to the conjecture.
Considering a ...
13
votes
8answers
2k views
We're much closer than you think
Martin Ender's 2D programming language Alice has two different modes depending on what orientation the IP has: orthogonal (Cardinal mode) or diagonal (Ordinal mode). Commands in Alice change their ...
20
votes
18answers
2k views
Eating Persistence
Intro
Find the result of number cannibalism.
Why was 6 scared of 7? Becase 7 8 9.
Your program will have to find the result of applying the ...
19
votes
16answers
2k views
Size up a number
Intro
Given a whole number \$< 100,\$ extend/shorten the english representation of the number to have as many characters as it's value.
Sandbox
Rules
Take the number \$n\$, and get it in words ...
11
votes
1answer
383 views
Amount Of Potential Keys That'll Fit The Lock
Introduction:
You're a key maker, and want to access something from a safe that has a lock. Unfortunately, the key to that lock is lost, so you'll have to make a new one. You have access to a bunch of ...
19
votes
13answers
1k views
sporeball numbers
Background
We've studied at least five different types of numbers based on the IDs of different users on this site. Why not study another?
My user ID is \$91030_{10}\$. Its binary representation is \$...
12
votes
13answers
1k views
Diophantine Approximation: find lowest possible denominator to approximate within given precision
Challenge
Given a number x and a precision e, find the lowest positive integer q such that <...
16
votes
12answers
2k views
Implement the Polygamma function
The Polygamma function of order \$m\$, \$\psi^{(m)}(z)\$, is the \$(m + 1)\$th derivative of the logarithm of the gamma function, which is also the \$m\$th derivative of the digamma function. Your ...
-6
votes
13answers
255 views
Number chopping: Split a number into its digits [closed]
Number Splitting
Instructions
Oh no, my numbers have stuck together! Luckily, we can split them apart with code.
Your code should be a function that takes an integer input from stdin or as an argument....
28
votes
36answers
3k views
Rotate a number
Given a positive number n, rotate its base-10 digits m positions rightward. That is, output the result of ...
9
votes
13answers
750 views
Descending dungeons of positional systems
The sequence discussed in this challenge is a variant of the Descending Dungeons sequence family. Specifically, the sequence generation rules:
...
31
votes
48answers
4k views
How many 1's we get
Description
Count how many occurrences there are of the digit 1 between two given numbers \$[a, b]\$, inclusive.
For example, from 1 to 100 it should be 21:
1, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19,...
7
votes
7answers
2k views
Music with pi and e
Because I forgot to celebrate the pi-day(14.3) lets celebrate with \$\pi\$, \$e\$ (Euler's number) and music!
Challenge
No, we don't have time to eat a pi-pizza, lets make a program.
What you need is ...
5
votes
8answers
248 views
Is it a geometric sequence or not? [closed]
Well, last time I asked for an arithmetic sequence, now comes the geometric sequence
Challenge
In this challenge, the input will be an unordered set of numbers and the program should be able to tell ...
-7
votes
4answers
210 views
Is it an Arithmetic Sequence or not? [closed]
Challenge
In this challenge, the input will be an ordered set of numbers and the program should be able to tell if the set of numbers is an Arithmetic Sequence.
Input
The input will be a list ...
13
votes
18answers
1k views
Name the Aztec year
It's time for another Mesoamerican calendar! The Xiuhnelpilli was used by the Aztecs (more properly, the Mexica) to name their years. Each year has a number and a sign. Here's part of the cycle:
<...
2
votes
3answers
282 views
Checking a Windows 95 OEM Key for validity [closed]
Introduction
Windows 95 used a very simple algorithm for verifying license keys. The scheme of an OEM license key always looked like this:
xxxyy-OEM-NNNNNNN-zzzzz
...
17
votes
11answers
2k views
The Double-Castle Numbersā¢
Introduction
A double-castle number™ is a positive integer number that has a pattern of $$\underbrace{a\cdots a}_{m\text{ }a\text{s}}b\underbrace{a\cdots a}_{m\text{ }a\text{s}}b\underbrace{a\...
42
votes
5answers
4k views
Compute xkcd's Wrong Times Table
The 2020-05-29 xkcd comic showed us the numbers that Randall Munroe feels would be most likely to result from multiplication, other than the correct answers. The table does seem to have some sort of ...
20
votes
17answers
1k views
Bubbler numbers
Background
My user ID is 78410, or \$1 0 0 1 1 0 0 1 0 0 1 0 0 1 0 1 0_2\$. One interesting property of this number is that, in binary,
it doesn't have three consecutive identical digits, and yet
it ...
12
votes
10answers
861 views
Find all Belphegor primes
A Belphegor number is a number of the form \$(10^{n+3}+666)*10^{n+1}+1\$ (1{n zeroes}666{n zeroes}1) where \$n\$ is an non-negative integer. A Belphegor prime is a ...
11
votes
22answers
1k views
7
votes
6answers
427 views
Build the smallest number
Given a non-empty list of digits 0 though 9, output the smallest number that can be produced by an expression formed by reordering these digits and introducing exponentiation signs ...
-2
votes
1answer
64 views
How to find the original value based on modulus/reminder and some other information [closed]
This might be a very basic question in terms of math,
x % constant = x_modulus
(x + some_number) % constant = y_modulus
Given the value of ...
5
votes
20answers
980 views
Calculate The Digit Sum
Your task is to get two numbers, and output the digit sum of them. We'll define digit sum as the following:
take the decimal (base 10) digits of each of them, and pad with 0s the shortest number (e.g....
17
votes
34answers
1k views
Binary Reduce a List By Addition With a Right Bias
Given a list of 2 or more strictly positive integers, sum the first and last half of the list, with the middle element being counted only in the right half if the list has an odd number of elements
...
9
votes
9answers
2k views
13
votes
5answers
454 views
Base-phi converter time!
The Golden Ratio Bureau is obsessed with this new thing they call base-phi. You see it and decide to code-golf, as is your natural instinct.
To be specific, base-phi is a number system like base 10, ...
25
votes
14answers
2k views
Evaluate Conway chained arrow notation
Background
Conway chained arrow notation is a notation to express very large numbers. It consists of zero or more positive integers separated by right arrows, e.g. \$2 \to 3 \to 4 \to 5 \to 6 \$.
...
15
votes
8answers
697 views
Multiple, Lit Plume, Mute Pill and so on
We say two positive integers are anagrams of each other if the digits in one of them (in decimal representation) can be rearranged to form the other. Leading zeros don't count. For example, 110020222 ...
20
votes
14answers
2k views
Donation arms race
The barfoos, a hypothetical alien species, go about charity in an interesting way.
Every morning, barfoo Specialists come up with an ordered list of causes to donate to, and for each cause they ...
17
votes
9answers
2k views
Missile-mounted cameras
You are employed as Administrator in charge of Road Maintenance and Planning. The intelligence division of the Agency for Road Maintenance and Planning has come up with a brilliant and not at all ...
15
votes
43answers
2k views
Generate list of numbers and their negative counterparts
A recent SO question asks for a convenient one-liner to generate a list of numbers and their negative counterparts in Python.
Given two integers \$1ā¤aā¤b\$, generate all the integers \$x\$ such that \$...
23
votes
11answers
2k views
Find a Similar Number
We consider two integers to be similar if, when written in decimal, have the same length, and if we compare characters in any two positions for both decimal strings, the comparison results (less, ...
19
votes
22answers
2k views
Convert to and from Base 94
The challenge
Make 2 programs which convert decimal to and from base 94, or a bidirectional program.
Base 94?
Base 94 is like any other base, but instead of 0 to 9 and letters, it uses ASCII ...
19
votes
24answers
2k views
3
votes
5answers
102 views
Find the binary period [duplicate]
We know that not all fractions have a terminating binary representation. However every fraction can be written as a leading portion followed by a repeating portion. For example \$1/3\$ starts with \$...
26
votes
9answers
789 views
Mad Libs number sequences
My robot for generating Mad Libs-style sequence challenges has gone rogue! To defeat it, I need you to write code that can solve all the challenges it can crank out.
Your input is three selections ...
25
votes
11answers
3k views
Any lips images
Introduction
The \$n\$-ellipse is a generalization of the ellipse with possibly more than two foci. Specifically, given \$n\$ points on the plane, called foci, the \$n\$-ellipse is the set of points ...
20
votes
8answers
1k views
Counting Distinct Real Roots of Low-Degree Polynomials
Challenge: I want to know about the real roots of polynomials. As a pure mathematician, I care about the existence of such roots, rather than their numeric values.
The challenge is to write the ...
23
votes
22answers
3k views
Find self-locating strings in a number
Based on this Numberphile video
A self-locating string is a number (or set of numbers) in a decimal expansion which corresponds to its location, from the start of the decimal.
For example, take the ...
16
votes
5answers
820 views
How many unique one sided polyominos
Context
From Wikipedia:
A polyomino is a plane geometric figure formed by joining one or more equal squares edge to edge.
one-sided polyominoes are distinct when none is a translation or rotation of ...
17
votes
37answers
2k views
Is it a doubling sequence?
A doubling sequence is an array of numbers where each subsequent number is at least twice the previous number.
Given an ordered list of numbers, determine if the numbers in the list (\$n_{x}\$) have ...
10
votes
5answers
191 views
Count switches in a smallest square root sequence mod \$2^n\$
Definition
For any \$a\equiv1\ (\text{mod }8)\$ and \$n\ge3\$, there are exactly 4 roots to the equation \$x^2\equiv a\ (\text{mod }2^n)\$. Now, let \$x_k(a)\$ be the smallest root to the equation \$...
14
votes
18answers
1k views
Find the Inverse Neighbor Pairs
Definition
We say a pair of integers \$(a,b)\$, where \$0<a<b<N\$ and \$N\$ is an integer larger than 4, is an inverse neighbor pair respect to \$N\$ if \$ab\equiv1\text{ }(\text{mod }N)\$ ...
19
votes
13answers
1k views
Number of palindrome splits
In this task you will take as input a non-negative integer \$n\$, and output the number of pairs of non-negative integers \$a,b\$ such that both are palindromes*, \$a \leq b\$, and \$a+b = n\$. For ...
21
votes
25answers
2k views
Power-Ending Patterns
When you look at the last decimal digit of each power of a non-negative integer a repeating pattern forms. For example, 3:
...
35
votes
35answers
6k views
Shift right by half a bit
The challenge is to implement a program or function (subsequently referred to as "program") that takes a nonnegative integer \$n\$ as input and returns \$n\over\sqrt{2}\$ (the input divided by the ...
25
votes
17answers
928 views
Cartesian LCM of two arrays
Given two nonempty arrays of natural numbers \$a\$ and \$b\$, return the shortest nonempty array of pairs of natural numbers \$q\$ such that the sequence of first elements of \$q\$ consists of a whole ...
