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

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14
votes
16answers
367 views

Determine the depth of an array

A simple challenge for your Monday evening (well, or Tuesday morning in the other half of the world...) You're given as input a nested, potentially ragged array of positive integers: [1, [[2, 3, ...
11
votes
15answers
2k views

Apply Kirchhoff's law

Kirchhoff's law says that when you sum up all the currents (positive for the currents going to a junction, and negative for current leaving a junction), you will always get as result 0. Look at the ...
25
votes
30answers
2k views

Find the largest and the smallest number in an array

The Task The task is very simple. Given an array containing only integers and strings, output the largest number and the smallest number. Test Cases Input: [1, 2, 3, 4, 5, 6, 7, 8] Output: 1, 8 ...
21
votes
4answers
267 views

Magnetic pull in an array

Background I have a row of powerful magnets and a bunch of metal objects between them. Where will the magnets pull them? Input Your input is an array of non-negative integers, which will contain at ...
14
votes
3answers
305 views

Check work periods

Introduction Here in Germany the ruling on work times is very strict. If you work 6 or more hours a day, you have to take at least a 30 minute break. If you work 9 or more hours, you need to take a ...
22
votes
37answers
2k views

Consolidate an Array

The task is simple: consolidate an array of ints. Consolidating this array consists of the following: All instances of 0 need to be moved to the end of the array. There should be no 0s between the ...
15
votes
12answers
549 views

Remove specified non-numeric rows

In case there's any doubt: Nan = Non-numeric datatype for the purposes of this challenge. Write a program or function that takes a matrix / array as input, as well as a list of column indices. ...
28
votes
14answers
2k views

Show the Top Five Comment Scores on a SE Post

A Stack Exchange script determines which five comments on questions or answers are initially seen on the main page of sites through the number of upvotes on them; the five comments with the highest ...
35
votes
20answers
3k views

Remove every N-th N

The task In this challenge, your input is a non-empty list of positive integers, given in the native format of your language. Your output is that same list, in the same format, with some elements ...
24
votes
7answers
974 views

Bouncing in an array

Introduction Arrays can also be seen as a field for a bouncing ball. This of course sounds very vague, so here is an example of an input: [1, 2, 3, 4, 5, 6, 7, 8, 9] [9, 8, 7, 6, 5, 4, 3, 2, 1] [1, ...
37
votes
32answers
9k views

Cheating a multiple choice test

Introduction While studying, I tried to come up with several ways to cheat a multiple choice test. It basically is a compressed version of the multiple choice answers. The method goes as following: ...
35
votes
13answers
4k views

Look, up in the sky! It's a super duper array!

Inspired by this question from our rivals friends over at Code Review. Definitions A super array is an array where each new element in the array is larger than the sum of all the previous elements. ...
9
votes
1answer
183 views

Sort scrambled two-dimensional array filled with numbers by swapping adjacent numbers [closed]

A two-dimensional array of size n×n is filled with n*n numbers, starting from number 1. Those numbers are to be sorted per row in ascending order; the first number of a row must be greater than the ...
18
votes
7answers
871 views

Find the capacity of 2D printed objects

In a fictional 2D world, a set of 2D printing instructions for an object can be represented by a list of integers as follows: 1 4 2 1 1 2 5 3 4 Each number represents the height of the object at ...
24
votes
21answers
1k views

Find ranges of True values in a list

Challenge: Write a function or program that accepts a list of boolean values and returns all of the ranges of True's. Test Cases: f [F] = [] f [T] ...
47
votes
9answers
3k views

Surrounded Countries

Countries own a series of territories on a 1D world. Each country is uniquely identified by a number. Ownership of the territories can be represented by a list as follows: 1 1 2 2 1 3 3 2 4 We ...
18
votes
1answer
367 views

Separate my integers

Introduction In the field of mathematics known as topology, there are things called separation axioms. Intuitively, you have a set X and a collection of subsets of X, which we can think of as ...
82
votes
15answers
3k views

Xorting an array

Conceptually, this challenge is really simple. You're given a list of non-negative integers ai. If possible, find a non-negative integer N, such that the list consisting of bi = ai XOR N is sorted. If ...
14
votes
2answers
199 views

Can the Array be Unshuffled?

Background Very skilled card handlers are capable of a technique whereby they cut a deck perfectly in half, then perfectly interleave the cards. If they start with a sorted deck and perform this ...
31
votes
36answers
2k views

Cover up zeroes in a list

Inspired by this SO question As input you will be given a non-empty list of integers, where the first value is guaranteed to be non-zero. To construct the output, walk from the start of the list, ...
32
votes
13answers
4k views

The sum is always 15

Write a program or function that takes an array of non-negative integers as input and outputs a set of vectors/arrays with the elements of the input array in order, split so that each vector sums up ...
23
votes
28answers
1k views

Separate a list into even-indexed and odd-indexed parts

Inspired by this question: Make a function (or a full program) that receives a list of numbers and outputs the list rearranged, so that even-indexed numbers appear first, and odd-indexed numbers ...
25
votes
8answers
775 views

Rotate the anti-diagonals

Background In most reasonable programming languages, it's very easy to rotate the rows or columns of a 2D array. In this challenge, your task is to rotate the anti-diagonals instead. Recall that the ...
14
votes
1answer
665 views

90° Self-Rotating Program

Introduction Write a complete program that rotates a rectangular block of ASCII characters 90 degrees clockwise. When the program itself is rotated 90 degrees clockwise, it rotates a block of ASCII ...
19
votes
2answers
256 views

Are these trees isomorphic?

Introduction In this challenge, your task is to write a program that decides whether two given trees are isomorphic. A tree means a directed acyclic graph where every node has exactly one outgoing ...
34
votes
35answers
4k views

Lossy Sorting (Implement Dropsort)

Dropsort, designed by David Morgan-Mar, is an example of a linear-time "sorting algorithm" that produces a list that is, in fact, sorted, but contains only some of the original elements. Any element ...
17
votes
11answers
630 views

Calculate the bounded cumulative sum of a vector

The cumulative sum of a vector is calculated by simply taking the sum of all previous elements. For instance: vec = [1 1 1 -1 -1 -1 -1 -1 1 1 1 1 -1] cum_vec = [1 2 3 2 1 0 -1 -2 -1 0 ...
22
votes
24answers
1k views

Iterated partial sums

The partial sums of a list of integers [a1, a2, a3, ..., an] are s1 = a1 s2 = a1 + a2 s3 = a1 + a2 + a3 ... sn = a1 + a2 + ... + an We can then take the list of partial sums [s1, s2, s3, ..., sn] ...
25
votes
15answers
1k views

Illustrate the square of a binomial

Given (by any means) two different natural numbers (of any reasonable size), output (by any means) the square of their sum as in the examples below: Given 4 and 3, output: 12 12 12 12 9 9 9 12 12 ...
12
votes
12answers
1k views

Play the elimination game

Introduction In this challenge, your task is to simulate a certain type of elimination game. In the game, the participants stand in a circle, and everyone is holding an integer. On each round of the ...
19
votes
1answer
193 views

One goes up, the other comes down

Introduction In this challenge, your task is to decide whether a given sequence of numbers can be separated into two subsequences, one of which is increasing, and the other decreasing. As an example, ...
17
votes
34answers
2k views

Non Unique Elements

Write a program which finds the non-unique elements of an array of signed integers. The resulting array can be in any order. Your answer may be a snippet which assumes the input to be stored in a ...
1
vote
3answers
208 views

Transpose columns in table

Let's say you've got a table of data: meter_id date 0000 0600 1200 1800 0 030915 10 20 30 40 1 030915 15 7 49 2 where the last four columns are meter readings at ...
13
votes
5answers
282 views

Is it L-convex?

Background A polyomino is called L-convex, if it's possible to travel from any tile to any other tile by an L-shaped path, that is, a path that goes in the cardinal directions and changes direction ...
16
votes
12answers
624 views

Integer Percentify

Write a function which takes in a list of positive integers and returns a list of integers approximating the percent of total for the corresponding integer in the same position. All integers in the ...
8
votes
4answers
513 views

Average Out Two Lists

Average out two lists Challenge Given two lists of positive integers, determine whether it is possible to rearrange the elements into two new lists such that the new lists have the same arithmetic ...
32
votes
12answers
4k views

The Will Rogers Phenomenon

The so-called Will Rogers phenomenon describes a way to tweak statistics by raising the average in two (multi)sets when one element is moved between the two sets. As a simple example, consider the two ...
24
votes
17answers
1k views

Calculating waves

I've been scrolling around this site for a while, but just recently got really interested in actually trying out some of the challenges. I was intending to try my hand at some of the existing ...
47
votes
25answers
5k views

First code golf decathlon

Tasks All competitors try to solve the following list of 10 tasks: math Read a positive integer n from input and return the sum of the cubes of the first n non-negative integers. For input 1, ...
16
votes
8answers
945 views

Analyzing Earthquakes

Background The Random Domino Automaton is a toy model for earthquakes, inspired by cellular automata. In this challenge, your task is to simulate a simplified version of this model, and collect data ...
20
votes
16answers
3k views

Bitstring Physics

Background Yes, bitstring physics is a real thing. The idea is to construct a new theory of physics using only strings of bits that evolve under a probabilistic rule... or something. Despite reading ...
19
votes
13answers
1k views

Refined Partitions

Consider an array of integers: [1, 0, 9, 1, 3, 8] There are a lot of ways to partition this list into consecutive sublists. Here are three: A: [[1, 0, 9], [1, 3, 8]] B: [[1], [0, 9], [1, 3], [8]] ...
9
votes
4answers
1k views

Calculate a probability exactly

This task is about writing code to compute a probability exactly. The output should be a precise probability written as a fraction in its most reduced form. That is it should never output 4/8 but ...
19
votes
9answers
1k views

Sum in each dimension

You are given a multi-dimensional array of integers. Each dimension has a fixed size (so that it would be always rectangular if it is 2D). Your program should calculate the sums in each dimension and ...
20
votes
15answers
2k views

Generalised Array Riffle

A simple golf to start the week! You're given three arrays: the base array B, the value array V and the index array I. You should produce another array where the values from V are inserted into B at ...
15
votes
10answers
696 views

Undirect a Graph

Introduction In this challenge, you are given a directed graph with self-loops, and your task is to convert it to an undirected graph without self-loops. Input Your input is a directed graph with ...
8
votes
12answers
938 views

Rearranging a set of numbers into order

The Question Given a set of 9 numbers, m[], which contains only numbers 1 through 9 in a random order, with no two numbers being the same, create a program in any language which rearranges the number ...
15
votes
9answers
2k views

Compute the Hausdorff Distance

Introduction The Hausdorff distance measures the difference between two subsets of a metric space. Intuitively, a metric space is just some set with a built-in distance function; in this challenge, ...
5
votes
2answers
239 views

Remove boxes under preservation of shape

This challenge is specific to languages of the APL family. Although it might be solvable in other languages, please do not expect this to be easy as it depends on some specific concepts of this ...
7
votes
5answers
652 views

IPV4 subnet list cleaner (in CIDR notation)

We have a lot of IPV4 address, to group into subnets, so we need a tool for doing this: Our list is very ugly, not ordered and sometime in subnet notation, sometime in simple address. Sample: ...