# Questions tagged [number]

This challenge is intended to be solved by using, manipulating, accepting as input, or outputting numeric values.

345 questions
42k views

### Is this number a prime?

Believe it or not, we do not yet have a code golf challenge for a simple primality test. While it may not be the most interesting challenge, particularly for "usual" languages, it can be nontrivial in ...
24k views

### Fibonacci function or sequence

The Fibonacci sequence is a sequence of numbers, where every number in the sequence is the sum of the two numbers preceding it. The first two numbers in the sequence are both 1. Here are the first ...
23k views

### Largest Number Printable

Your goal is to write a program that prints a number. The bigger the number, the more points you'll get. But be careful! Code length is both limited and heavily weighted in the scoring function. Your ...
923 views

### Base Conversion With Strings

Introduction We've have a few base conversion challenges here in the past, but not many designed to tackle arbitrary length numbers (that is to say, numbers that are long enough that they overflow ...
2k views

### Say What You See

The "Look and say" or "Say what you see" sequence is a series of numbers where each describes the last. ...
11k views

### The Versatile Integer Printer

Write a piece of code that is executable in at least three different languages. The code must output the integer 1 in language number one, ...
12k views

### Sum of all integers from 1 to n

I'm honestly surprised that this hasn't been done already. If you can find an existing thread, by all means mark this as a duplicate or let me know. Input Your input is in the form of any positive ...
7k views

### Notcalc (Calculate the wrong answer)

Goal: Given two natural numbers (integers from 0 to infinity), output a number that is not the sum of those numbers, but is a natural number. Example solutions (TI-Basic): ...
4k views

### Generate a Kolakoski sequence [duplicate]

Definition1 A Kolakoski sequence is a self-describing infinite sequence {kn} of alternating blocks of 1's and 2's, given by the following rules: k0 = 1 kn = the length of the (n+1)'th ...
5k views

### Balanced Ternary Converter

Credits for the challenge idea go to @AndrewPiliser. His original proposal in the sandbox was abandoned and since he has not been active here for several months, I have taken over the challenge. ...
6k views

### Golf a number bigger than TREE(3)

The function TREE(k) gives the length of the longest sequence of trees T1, T2, ... where each vertex is labelled with one of k colours, the tree Ti has at most i vertices, and no tree is a minor of ...
12k views

### Count up forever

Write a program that counts up forever, starting from one. Rules: Your program must log to STDOUT or an acceptable alternative, if ...
5k views

### Generate Monday Numbers

Monday numbers, as defined by Gamow in this question over on Puzzling, are positive integers N with the following three properties: The decimal representation of N does not contain the digit 0 The ...
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 ...
2k views

### Different Way Forward

Given a list of integers produce a Forward Difference at a specified order/depth. For the list of integers: (10, 18, -12, 4, 8, -3, -5, 67, 9, 14) The Forward ...
3k views

### Find the number in the Champernowne constant

Introduction In base 10, the Champernowne constant is defined by concatenating representations of successive integers. In base 10: 0.1234567891011121314151617... ...
6k views

### Turn an integer n into a list containing it n times

Given an integer n as input, return a list containing n, repeated n times. For example, the ...
16k views

### What is the smallest positive base 10 integer that can be printed by a program shorter (in characters) than itself?

I think the question as above is clear, but just in case: Write a full program (not just a function) which prints a positive base 10 integer, optionally followed by a single newline. Qualifying ...
12k views

### Outputting ordinal numbers (1st, 2nd, 3rd)

I would like to generate (as a return result of a function, or simply as the output of a program) the ordinal suffix of a positive integer concatenated to the number. Samples: ...
6k views

### It's Hip to be Square

Challenge So, um, it seems that, while we have plenty of challenges that work with square numbers or numbers of other shapes, we don't have one that simply asks: Given an integer ...
4k views

### Flipping pancakes

In pancake sorting the only allowed operation is to reverse the elements of some prefix of the sequence. Or, think of a stack of pancakes: We insert a spatula somewhere in the stack and flip all the ...
3k views

### Generate a pair of integers from a non-negative one

You should write a program or function which takes a non-negative integer N as input and outputs or returns two integers (negative, zero or positive) ...
1k views

### Prime factors buddies

Given an integer N > 1, output all other numbers which prime decompositions have the same digits as the prime decomposition of ...
1k views

### Compute the number of ways how you can express a number as a sum [closed]

For a given natural number n, compute the number of ways how one can express n as a sum of positive natural numbers. For example,...
3k views

### Is it a balanced number?

A number is balanced if the sum of the digits on each half of the number is equal, so: 1423 is balanced because 1+4 = 2+3, so is:...
1k views

### Natural construction

The natural numbers including 0 are formally defined as sets, in the following way: Number 0 is defined as the empty set, {} For n ≥ 0, number n+1 is defined as n ∪ {n}. As a consequence, n = {0, 1, ...
779 views

### Dames, do some math!

The order of operations, PEMDAS, is a basic rule in mathematics telling us which order operations should be performed: "Parentheses, Exponents, Multiplication and Division, and Addition and ...
2k views

### Implement t9-like functionality

Your challenge today is to implement a t9-like functionality. You will implement a function that will only have 2 parameters. You will receive 1 phone number in a string and the content of a text ...
570 views

### Determine the position of a non-negative number in the infinite spiral

Definition The infinite spiral used in this question has 0 on the position (0,0), and continues like this: ...
2k views

### Mixed Base Conversion

Background Most people on here should be familiar with several base systems: decimal, binary, hexadecimal, octal. E.g. in the hexadecimal system, the number 1234516 would represent ...
21k views

### How high can you count?

Challenge: Your task is to write as many programs / functions / snippets as you can, where each one outputs / prints / returns an integer. The first program must output the integer ...
13k views

### Hyperprogramming: N+N, N×N, N^N all in one

Write a program that takes in a number N from 1 to 9 inclusive. In its native form your program should output N+N. E.g. output 2 if N is ...
11k views

### Print numbers from 1 to 10

This might be a very simple challenge, but I am surprised it hasn't been done on code-golf yet: Print all Integers from 1 to 10 inclusive in ascending order to standard output. Your output format ...
2k views

### Encode an integer

Given positive integer n > 2. We convert it to an array as follows: If it is equal to 2 return an empty array Otherwise ...
9k views

### List Prime Numbers [duplicate]

Introduction Prime numbers are simple, right? Well, now you get your chance to find out! Challenge You must write a program or function that takes an input n and ...
3k views

### Monday Mini-Golf #1: Reverse Fibonacci Solver

Monday Mini-Golf: A series of short code-golf challenges, posted (hopefully!) every Monday. A Fibonacci-like sequence is obtained using the same method as the famous Fibonacci sequence; that is, each ...
2k views

### Spell out numbers in French

There was a challenge to convert a number to its numeral in English, but that was too straightforward. Given a number 0–100, your task is to output the corresponding numeral in French. The French ...
3k views

### Count trailing truths

Inspired by, and in memory of, my dear friend and colleague, Dan Baronet, 1956 – 2016. R.I.P. He found the shortest possible APL solution to this task: Task Given a Boolean list, count the number ...
7k views

### Print all integers

Write a program or function which will provably print all integers exactly once given infinite time and memory. Possible outputs could be: ...
7k views

### Output the sign

Given a number N, output the sign of N: If N is positive, output 1 If N is negative, output -1 If N is 0, output 0 N will be an integer within the representable range of integers in your chosen ...
2k views

### Convert number to a base where its representation has most “4”s

Inspired by this. There is a number, given as either integer, string or array of digits (your choice). Find the base in which the representation of the number will have most "4"s and return that base. ...
3k views

### Find the next 1-sparse binary number

A positive integer N is K-sparse if there are at least K 0s between any two consecutive 1s in its binary representation. So, the number 1010101 is 1-sparse whereas 101101 is not. Your task is to ...
1k views

### The Coin Problem

Background The official currency of the imaginary nation of Golfenistan is the foo, and there are only three kinds of coins in circulation: 3 foos, 7 foos and 8 foos. One can see that it's not ...
808 views

### Shortest representation of an Underload number

Flavour text The stack-based esolang Underload has some interesting ties to functional programming. One of them is its treatment of the numerical datatype—like the lambda calculus, you ...
6k views

### Find the Pisano Period

The Fibonacci sequence is a well know sequence in which each entry is the sum of the previous two and the first two entries are 1. If we take the modulo of each term by a constant the sequence will ...
552 views

### Find the missing number in an undelimited string

The challenge is to identify the missing number in a string of undelimited integers. You are given a string of digits (valid input will match the regular expression ...
932 views

### Largest and smallest values from concatenated integers

This problem is from Five programming problems every Software Engineer should be able to solve in less than 1 hour which itself is an interesting read. The first few problems are trivial, but the ...
517 views

### Polygonal Numbers!

Introduction In mathematics, a polygonal number is a number represented as dots or pebbles arranged in the shape of a regular polygon. The dots are thought of as alphas (units). These are one type ...