Questions tagged [integer]

For challenges involving the manipulation of integers.

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12
votes
31answers
2k views

Determine the Winner of a Game of Australian Football

In Australian Football, goals are worth 6 points and behinds are worth 1 point. Scores may include the number of goals and behinds, as well as the total score. Given the number of goals and behinds ...
31
votes
29answers
5k views

Double it your way

There have been a couple of challenges involving doubling source code: here and here. The task we have here is a bit harder, but should be doable in almost every language. In this challenge, you will ...
26
votes
17answers
4k views

Infinitely many primes

Since Euclid, we have known that there are infinitely many primes. The argument is by contradiction: If there are only finitely many, let's say \$p_1,p_2,...,p_n\$, then surely \$m:=p_1\cdot p_2\cdot.....
22
votes
24answers
4k views

Count the number of triangles

Given a list of positive integers, find the number of triangles we can form such that their side lengths are represented by three distinct entries of the input list. (Inspiration comes from CR.) ...
18
votes
30answers
2k views

Numbers Decrease while Letters Increase

Randomly inspired by Numbers Increase While Letters Decrease Given a list of mixed letters and integers (e.g., ['a', 2, 3, 'b']) increase the letters by one ...
26
votes
30answers
3k views

Output with the same length always

With challenges like Output with the same length as the code and Create output twice the length of the code, I thought of a separate, but similar challenge. The task is to produce an output. It can ...
9
votes
0answers
169 views

Decompose Commutators

A theorem in this paper1 states that every integral n-by-n matrix M over the integers with trace M = 0 is a commutator, that means there are two integral matrices A,B of the same size ...
34
votes
35answers
5k views

Repeated! Factorials!

Not to be confused with Find the factorial! Introduction The factorial of an integer n can be calculated by $$n!=n\times(n-1)\times(n-2)\times(...)\times2\times1$$...
27
votes
28answers
4k views

Inverse Colombian Function

Let's define a sequence: The n digit summing sequence (n-DSS) is a sequence that starts with n. If the last number was k, then the next number is k + digit-sum(k). Here are the first few n-DSS: ...
5
votes
4answers
423 views

Find X,Y,Z coordinates from index

Introduction I began studying the Collatz Conjecture And noticed these patterns; 0,1,2,2,3,3...A055086, and 0,1,2,0,3,1...A082375, in the numbers that go to 1 in one odd step, 5,10,20,21,40,42......
23
votes
24answers
3k views

Robbers: The Hidden OEIS Substring

This is a Cops and Robbers challenge. This is the robber's thread. The cop's thread is here. The cops will pick any sequence from the OEIS, and write a program p that prints the first integer from ...
37
votes
27answers
4k views

Cops: The Hidden OEIS Substring

This is a Cops and Robbers challenge. This is the cop's thread. The robber's thread is here. As a cop, you must pick any sequence from the OEIS, and write a program p that prints the first integer ...
25
votes
54answers
6k views

Integer Lists of Noah

Introduction: I think we've all heard of it, but here a very brief summary: Noah gathered two of every species of animal on the planet, male and female, to save in his Ark during a great flood. The ...
2
votes
3answers
115 views

Sum of multiples of powers of ten of an integer [duplicate]

Write a function to produce, for a non-negative integer, a string containing a sum of terms according to the following: ...
-6
votes
4answers
188 views

Is this number a palindrome? [closed]

Input A single integer in your language's preferred format. This format is non-negotiable (no input as strings, arrays of digits, etc.), but standard I/O formats do apply if otherwise it would be ...
37
votes
31answers
14k views

Do the 26 richest billionaires own as much wealth as the poorest 3.8 billion people?

Introduction: A few days ago I read this post with the same title when I came across it in the HNQ. In this question it is being discussed if the claim of president-candidate Bernie Sanders, who ...
43
votes
12answers
3k views

Prime parity peregrination

The purpose of this challenge is to graphically depict a walk on the plane, where the direction of each step \$k\$ is determined by the primality of \$k\$ and the parity of its binary expansion. ...
5
votes
0answers
179 views

Fastest way to iterate over sublattice of discrete lattice

I need to construct a functor that iterates over the linear representation of a sub-lattice of size \$d_x,d_y,d_z,d_q\$ embedded in a lattice of size \$n_x,n_y,n_z,n_q\$. The sub-lattice corner is ...
21
votes
6answers
978 views

Subtract the Folded Matrix

Challenge: Given an NxN matrix where \$N\geq2\$ and one of eight distinct 'folding options', output a 2D array/list with the subtracted values. The eight folding options are: left-to-right; right-to-...
11
votes
6answers
862 views

Group Integers by Originality

Introduction: I collect twisty puzzles. Most twisty puzzles are produced and sold by Chinese companies. Most well-known companies ask permission from puzzle designers to produce their designs and ...
20
votes
22answers
2k views

Rotated Position of Integers

Challenge: Input: A sorted list of positive integers. Output: The amount of integers which are still at the exact same index, after rotating the digits in each integer its index amount of times ...
8
votes
4answers
610 views

Leading and Suffering Numbers

Introduction: In Dutch, the words leading and suffering, being 'leiden' and 'lijden' respectively, are pronounced the same way. One is written with a "short ei", and one with a "long ij", as we ...
20
votes
9answers
1k views

Warped chessboard

This challenge is about building a chessboard in which the square size, instead of being constant across the board, follows a certain non-decreasing sequence, as described below. The board is defined ...
32
votes
21answers
2k views

A ​Note ​on ​N!

J. E. Maxfield proved following theorem (see DOI: 10.2307/2688966): If \$A\$ is any positive integer having \$m\$ digits, there exists a positive integer \$N\$ such that the first \$m\$ digits of \$...
-2
votes
6answers
247 views

Map values to any multidimensional array [closed]

Codegolf challenge - mapping values in a multidimensional array [ [0, 0, 0], [0, 0, 0], [0, 0, 0] ] This 2D array is sick of being so false, and wants to ...
23
votes
20answers
1k views

Maximum summed subsequences with non-adjacent items

Introduction: Inspired by these two SO questions (no doubt from the same class): print the elements in the subarray of maximum sum without adjacent elements java and Maximum sum of non adjacent ...
11
votes
6answers
1k views

Area of a 2D convex hull

You are given an array/list/vector of pairs of integers representing cartesian coordinates \$(x, y)\$ of points on a 2D Euclidean plane; all coordinates are between \$−10^4\$ and \$10^4\$, duplicates ...
27
votes
13answers
3k views

Valid Badminton Score?

Introduction: I saw there was only one other badminton related challenge right now. Since I play badminton myself (for the past 13 years now), I figured I'd add some badminton-related challenges. ...
26
votes
22answers
2k views

The Digit Triangles

Challenge: Input: A positive integer \$n\$ Output: Create a list in the range \$[1,n]\$, and join it together to a string (i.e. \$n=13\$ would be the string ...
31
votes
23answers
8k views

Could you please stop shuffling the deck and play already?

Challenge: Input: A list of distinct positive integers within the range \$[1, \text{list-size}]\$. Output: An integer: the amount of times the list is riffle-shuffled. For a list, this means the ...
14
votes
11answers
885 views

Source permutation

A permutation of a set \$S = \{s_1, s_2, \dotsc, s_n\}\$ is a bijective function \$\pi: S \to S\$. For example, if \$S = \{1,2,3,4\}\$ then the function \$\pi: x \mapsto 1 + (x + 1 \mod 4)\$ is a ...
11
votes
31answers
774 views

Sum integers in a string

Input A string. Output The sum of all integers in the line. Constraints 1≤Length of line≤500 Sample test Case Input the 5is 108 seCONd4 a Output ...
33
votes
5answers
8k views

Historical difference between `/` and `÷` in mathematical expressions

Introduction: Inspired by a discussion that is already going on for many years regarding the expression \$6÷2(1+2)\$. With the expression \$6÷2(1+2)\$, mathematicians will quickly see that ...
7
votes
7answers
540 views

Check type of an integer

You will receive an integer less than 2000000000 and bigger than -2000000000 and you have to test what type(s) of number this is out of: ...
4
votes
9answers
287 views

Floating over the integers

As you may know, the typical binary floating point numbers in a computer language are quite different than the typical integer numbers in a computer language. Floating point numbers can represent a ...
20
votes
17answers
2k views

Square Root Distance from Integers

Given a decimal number k, find the smallest integer n such that the square root of n is ...
19
votes
25answers
2k views

The Highest Dice

Challenge: Here we have the first 100 items of a sequence: ...
23
votes
3answers
2k views

The Path Of The Wildebeest

Golf a program or function which gives the \$n^{\text{th}}\$ location of the wildebeest who starts at square \$1\$ on an infinite chessboard which is numbered in an anti-clockwise square spiral, where ...
24
votes
15answers
3k views

Matrix Jigsaw Puzzles

Input: An integer n Two equal-sized square matrices (with their width/height being a multiple of n) Output: One of two ...
27
votes
41answers
2k views

Enumerate each series of identical numbers in-place

Given a list of strictly positive integers, go through each distinct number and replace all occurrences of it with successive indices (zero or one based) of a new series. Examples ...
23
votes
18answers
2k views

Collapsing numbers

Let's define the a function on natural numbers \$n\$, written as base 10 digits \$d_k\; d_{k-1}\; \dotsc\; d_1\; d_0\$, as follows: As long as there are equal adjacent digits \$d_i\;d_{i-1}\$, ...
22
votes
13answers
3k views

Eight coins for the fair king

This is a "counterpart" of another puzzle, Eight coins for the fair king on Puzzling.SE. You can read the above puzzle for the background. The details about this puzzle are as follows. A set of 8 ...
21
votes
26answers
2k views

Digital Sumorial

Given an input n, write a program or function that outputs/returns the sum of the digital sums of n for all the bases 1 to ...
25
votes
6answers
1k views

Prime containment numbers (speed edition)

This is sequence A054261 The \$n\$th prime containment number is the lowest number which contains the first \$n\$ prime numbers as substrings. For example, the number \$235\$ is the lowest number ...
21
votes
14answers
2k views

Prime containment numbers (golf edition)

This is sequence A054261. The \$n\$th prime containment number is the lowest number which contains the first \$n\$ prime numbers as substrings. For example, the number \$235\$ is the lowest number ...
23
votes
25answers
2k views

Sort by Largest Digit(s)

Challenge: Given a list of integer, sort descending by their single largest digit(s). The order for numbers with the same largest digit are then sorted by second largest digit, etc. We ignore ...
17
votes
10answers
2k views

Reciprocal copycats

Let \$A\$ be a positive integer consisting of \$n\$ decimal digits \$d_1,d_2,...,d_n\$. Let \$B\$ be another positive integer. For the purpose of this challenge, we call \$A\$ a copycat of \$B\$ if ...
24
votes
15answers
2k views

All the single eights

Given a non-empty rectangular array of integers from 0 to 9, output the amount of cells that are ...
10
votes
9answers
1k views

Through Space and Time

Introduction: In general we usually speak of four dimensions: three space dimensions for x, y, and ...
15
votes
45answers
2k views

Print the Lost numbers

As a big fan of the Lost TV series, I always got intrigued by the sequence of numbers that repetitively appears on the episodes. These numbers are: \$ 4, 8, 15, 16, 23, 42\$ (A104101) Using any ...