Questions tagged [number]

A competition to solve a particular problem through the usage and manipulation of numbers.

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6 votes
16 answers
811 views

Written Word Equation

Word equations, but not as you know it! Given a sentence which will include two numbers, numerically, and a spelt operator, in the order seen in the examples, your goal is to give the numerical answer ...
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  • 1,682
20 votes
18 answers
2k views

Adaptive randomisation

Given a number \$n ≥ 2\$, a blackbox function \$f\$ that takes no arguments and returns a random integer in the range 0...n-1 inclusive, and a number \$m ≥ n\$, your challenge is to generate a random ...
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  • 30.5k
11 votes
32 answers
1k views

Index and return 3 characters

The challenge is simple: Read 3 letters from a system input¹ and convert them to numbers (A-1, B-2, C-3...Z-26)². Print each of those numbers in the order the ...
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  • 261
4 votes
3 answers
396 views

Will the hydra finally die? Part II

Background This is a follow up question to the question: Will the Hydra finally die? As before a dangerous A Medusa have released a dangerous Hydra which is revived unless the exact number of heads it ...
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19 votes
10 answers
1k views

Ploughed fields via moduli

Let \$R, C\$ be positive integers and let \$0 < s \leq 1\$. Consider the \$R \times C\$ matrix \$\mathbf M\$ defined as \begin{equation} M(i,j) = \frac{\mathrm{mod}\,(j, i^s)}{R^s}, \quad i = 1, \...
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  • 99.5k
15 votes
10 answers
3k views

Project Euler 1: Multiples in constant time

The purpose of this challenge is to solve the original first Project Euler problem, but as the title suggests in constant time (with respect to the size of the interval). Find the sum of all the ...
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30 votes
14 answers
2k views

Is it a Giuga number?

Giuga numbers (A007850) are composite numbers \$n\$ such that, for each prime factor \$p_i\$ of \$n\$, \$p_i \mid \left( \frac n {p_i} -1 \right)\$. That is, that for each prime factor \$p_i\$, you ...
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4 votes
9 answers
2k views

Will the Hydra finally die?

Background A Medusa have released a dangerous Hydra which is revived unless the exact number of heads it have is removed. The knights can remove a certain number of heads with each type of attack, and ...
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21 votes
16 answers
2k views

Largest Number with No Repeating Digit Pairs

Inspired by the problem with the same name on Puzzling SE by our very own Dmitry Kamenetsky. You are to find the largest number that only uses every digit pair once, in a given base. For example, in ...
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  • 1,921
29 votes
33 answers
2k views

Mr. Binary Counterman

Mr. Binary Counterman, son of Mr. Boolean Masker & Mrs. Even Oddify, follows in his parents’ footsteps and has a peculiar way of keeping track of the digits. When given a list of booleans, he ...
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  • 1,921
25 votes
12 answers
2k views

Collatz's ice cream cone factory

The Collatz sequence Given a positive integer \$a_1\$, the Collatz sequence with starting value \$a_1\$ is defined as \begin{equation} a_{n+1} = \begin{cases} a_n/2 & \mathrm{if}\ a_n\ \mathrm{is}\...
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  • 99.5k
8 votes
10 answers
608 views

A triangle of numbers

Challenge Make a triangle of numbers like below. How to? Let say we get a numbers in the form of ab, for example 12. We then create a triangle like below: Sorry ...
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11 votes
13 answers
706 views

'Plane' the numbers in any base!

Inspired by this Numberphile video. What is planing? In order to 'plane' a sequence of digits, you need to: Identify the lengths of the 'runs' (adjacently repeated digits) in the sequence. Non-...
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12 votes
7 answers
773 views

Prime Factorization - but on the exponents too

Though there is a prime factorization challenge and it's here, this, I feel, will be a bit more interesting than that one. To understand this, let's have an example; I will use 5,184 for this. \$5184 =...
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3 votes
3 answers
604 views

Programming Less-Than, Greater-Than and Equal-To functions using Restricted Source [closed]

I'm currently working with a branchless language which does not have native Less-Than, Greater-Than or Equal-To functions. I do however have min, ...
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11 votes
15 answers
700 views

Calculate \$ \lfloor n \log_2(n) \rfloor \$, exactly

Given an integer \$ n \ge 2 \$, you need to calculate \$ \lfloor n \log_2(n) \rfloor \$, assuming all integers in your language are unbounded. However, you may not ignore floating-point errors - for ...
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18 votes
9 answers
1k views

Dimensional Chess positions

Task Any one of these two: Determine if a given position (an ordered non-empty collection of integers in the range ‒8 to 8, or ‒7 to 7 if you want) is a valid Dimensional Chess position. List all the ...
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  • 27.7k
15 votes
15 answers
1k views

Convert version string to pack_format

When making a Minecraft data/resource pack, you need to include a pack.mcmeta file, which specifies information about it. ...
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11 votes
5 answers
441 views

Set the sum and product

Given two positive reals \$a\$ and \$b\$, output some positive reals \$r_i\$, such that \$\sum r_i=a\$ and \$\prod\left(r_i+1\right)=b\$. You can assume that it's possible. You can also assume that ...
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  • 12.8k
17 votes
3 answers
598 views

Compute the uncomputable ... sort of

Implement a function \$f\$ (as a function or complete program), such that \$ \displaystyle\lim_{n\rightarrow \infty} f(n) \$ converges to a number which is not a computable number. Answers will be ...
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  • 88.3k
5 votes
12 answers
922 views

Base-ically Guard

Base: part 1 This is part 2, Strongly suggest you go try out the first one if you haven't tried it. Story As one of the solvers, You've managed to get to the door of the base heaven. In front of the ...
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  • 1,367
23 votes
34 answers
2k views

Apply at indices

Given: a blackbox function \$f : \mathbb N \to \mathbb N\$, a list of positive integers \$L\$, and a list of indices \$I\$, apply \$f(x)\$ to the elements of \$L\$ at the indices specified in \$I\$. ...
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21 votes
9 answers
2k views

What's my lucky factor?

Lucky numbers (A000959) are numbers generated by applying the following sieve: Begin with the list of natural numbers: ...
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11 votes
21 answers
3k views

Exciting Mario Kart Grand Prix - Minimize the point difference!

Introduction When playing Mario Kart the other day, an interesting question popped up when a Grand Prix with my 2 roommates, 9 AI drivers and myself seemed to be fairly close and therefore exciting ...
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8 votes
17 answers
1k views

Base-ically god

Story The god of base is opening heaven’s gate for mortals to join the base party. You, as one of the believers, want to follow their steps to ascend to heaven. But not everyone can get in. The god ...
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  • 1,367
15 votes
19 answers
2k views

Do I need a win streak?

You have played \$N\$ matches in some game where each match can only result in one of the two outcomes: win or loss. Currently, you have \$W\$ wins. You want to have a win percentage of \$P\$ or more, ...
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  • 4,920
20 votes
6 answers
1k views

You are kinda Replacable to Me

You are provided with a non-empty array \$A\$ of integers, all greater than 0. But what good is an array if the elements do not sum up to the number \$N\$ (also provided as input)... So to change that,...
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  • 4,920
1 vote
4 answers
213 views

A problem of rarity [closed]

Given a positive input \$n > 0\$, output the amout of two types based on their rarity. The two types are called \$A\$ and \$B\$, we know the followings: \$n\$ is a limited input and the maximum is ...
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22 votes
20 answers
2k views

Code the Levine sequence

Introduction Note that I learned it from a Numberphile Video, where Neil Sloane explains it better. I recommend you to watch his Video. But for a quick Introduction: The Levine Sequence is made from ...
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  • 4,433
27 votes
31 answers
4k views

Count all possible Tweets

Challenge This challenge is pretty simple: Output the total number of possible Tweets. Given the fact that \$1{,}114{,}112\$ Unicode characters exist, and Tweets can be up to \$280\$ characters long, ...
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  • 5,913
25 votes
10 answers
1k views

Unique half rainbows

If we take a positive integer \$n\$ and write out its factors. Someone can determine \$n\$ just from this list alone. In fact it is trivial to do this since the number is its own largest factor. ...
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  • 88.3k
19 votes
16 answers
2k views

Self-Replicating Numbers

Background For the purpose of this challenge, all numbers and their string representations are assumed to be in decimal (base 10). I tried to find proper terminology for this challenge, but I do not ...
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16 votes
30 answers
1k views

Largest power of 2 that divides \$n\$

Related, related Introduction The ruler sequence is the sequence of the largest possible numbers \$a_n\$ such that \$2^{a_n}\mid n\$. It is so-called because its pin plot looks similar to a ruler's ...
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  • 5,913
17 votes
17 answers
1k views

Liars and Guessers

Github You have probably played, and may even have written a program to play, a simple number guessing game. If so, this probably looks familiar: ...
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  • 842
-3 votes
8 answers
973 views

Let's rise higher [closed]

Challenge The main objective of the challenge is pretty simple, this is an answer chaining contest, where you have to serially print numbers from 1. That means User 1's answer will print ...
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  • 11.9k
30 votes
24 answers
2k views

First sequence with no square differences

Consider the sequence \$(a_n)\$ defined in the following way. \$a_0=0\$ For all \$n=1, 2, 3, \dots\$, define \$a_n\$ to be the smallest positive integer such that \$a_n-a_i\$ is not a square number, ...
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  • 2,949
24 votes
34 answers
2k views

Remove excessive occurrences

Given an array \$A\$ of positive integers between \$1\$ and \$9\$ inclusive and a positive integer \$n\$, remove all integers in \$A\$ which appear more than \$n\$ times. For example: ...
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57 votes
137 answers
14k views

Print 0 to 100 without 1-9 characters

Print 0 to 100 without using characters 1,2,3,4,5,6,7,8,9 in your code. Seperator of numbers can be comma, whitespace or newline. Shortest code wins.
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12 votes
6 answers
799 views

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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  • 4,110
47 votes
24 answers
4k views

Ginormous number

Output this 1364-digit base-10 number: ...
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  • 137k
16 votes
8 answers
753 views

Close(st) Binary Boxes

Challenge: Given a list of non-negative integers, determine by how much you should increase each item to create the closest binary box with the resulting integer-list. What is a binary box? A binary ...
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13 votes
21 answers
1k views

Get the length of a Sumac Sequence

Heavily based on this closed challenge. Codidact post, Sandbox Description A Sumac sequence starts with two non-zero integers \$t_1\$ and \$t_2.\$ The next term, \$t_3 = t_1 - t_2\$ More generally, \$...
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  • 25.2k
15 votes
14 answers
1k views

Split a number in every way possible way within a threshold

Task Given a positive integer number and a threshold, split into every possible way without generating any numbers above the threshold. Examples Input: 15008 Threshold: 400 Valid Output: ...
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  • 253
4 votes
5 answers
301 views

Strobogrammatic Numbers [duplicate]

Strobogrammatic Numbers Definition A number which is rotationally symmetrical, i.e., it'll appear the same when rotated by 180 deg in the plane of your screen. The following figure illustrates it ...
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  • 2,860
21 votes
25 answers
1k views

Possible binaries sum

This challenge is inspired by the AoC 2020, Day 14 - Part II, created by Eric Wastl and his team, which asks to output the possible binary values from a bitmask. Let's say we've a bitmask like ...
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  • 2,860
23 votes
3 answers
703 views

Towering Cistercian representation

SE Sandbox Link, Codidact Sandbox Link Inspired by this video. Given a positive integer, draw its Cistercian representation as ascii art. The Challenge Cistercian numerals are a decimal-based number ...
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  • 25.2k
26 votes
17 answers
3k views

Convert negadecimal to decimal (and back)

Negadecimal, also known as base -10, is a non-standard positional numeral system. Take the number \$1337_{10}\$. In decimal, this has the value one thousand three hundred thirty seven, and can be ...
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12 votes
7 answers
2k views

Fastest square root of an arbitrary size

We do seem to have a fastest square root challenge, but it's very restrictive. In this challenge, your program (or function) will be given an arbitrarily sized nonnegative integer, which is the square ...
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19 votes
32 answers
3k views

Make a minimal and maximal 2-digit number from digits of two 3-digit numbers

Let's solve this user's homework; I think it's an interesting exercise! Input Two 3-digit natural numbers. Outputs Two 2-digit numbers. In each of the output numbers, one digit is taken from one input ...
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  • 12k
11 votes
14 answers
875 views

Prefix divisibility

Inspiration Given a positive integer \$1 \le n \le 9\$, output all positive \$n\$-digit integers \$i\$ for which the following is true: Each digit from \$1\$ to \$n\$ appears exactly once in \$i\$. ...
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