# Questions tagged [number]

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

1,179 questions
Filter by
Sorted by
Tagged with
1k views

### Write a number in overflowed binary

We all know how binary conversion works: the sequence of bits $$b_1, b_2, ..., b_{n-1}, b_n$$ encodes the number  b_1 \times 2^{n-1} + b_2 \times 2^{n-2} + ... + b_{n-1} \times 2^1 + b_n \times 2^...
212 views

### Check for Wonky numbers [closed]

Task : Wonky numbers are 3-or-more digit numbers that meet one or more of the following criteria: Any digit followed by all zeros: 100, ...
2k views

### Constructing Solar Panels from Squares

I'm designing a new space station for generic super-villain purposes (something something megalaser), but I'm having trouble designing the solar panels. My genius team of scientists can calculate ...
1k views

### Verb arities in J trains

Background J has trains similar to APL's. Given a sequence of verbs (functions), three rightmost verbs are grouped to form a derived verb (a fork) recursively, until one or two verbs remain. If the ...
1k views

### Find the k-th order summary of a number

Background The summary of a non-negative integer $n$ is the concatenation of all digits that appear in $n$ in increasing order, with each digit being preceded by the number of times it appears in \...
79 views

### Make me equal to 24 [duplicate]

Based on this game. Description : Based on Wikipedia's description. The 24 Game is an arithmetical card game in which the objective is to find a way to manipulate four integers so that the end result ...
2k views

### Find the smallest solution for this simple equation

Input 4 integers w, x, y, z from the range -999 to 999 inclusive where none of the values is 0. Output 4 integers a, b, c, d so that aw + bx + cy + dz == 0 where none of the values is 0. Restrictions ...
2k views

### Swap Two Values in a List

Introduction: Although we have a lot of challenges where swapping two items in a list is a subtask, like Single swaps of an array; Swap to Sort an Array; $n$ swaps into a nop; etc., we don't have ...
8k views

### Increment The Time

Every digital clock contains a small creature that has to advance the time every minute [citation needed]. Due to the popularty of digital clocks and the popularity of catching them in the wild, they ...
555 views

### Khinchin's constant bad estimate [closed]

Inspired by How to write down numbers having an infinity of decimals? Link 🇫🇷 Background From Wikipedia: for almost all real numbers $x$, coefficients $a_i$ ...
799 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 ...
2k views

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 ...
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 ...
389 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 ...
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, \...
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 ...
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 ...
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 ...
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 ...
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 ...
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}\...
592 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 ...
700 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-...
749 views

13k 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.