# Questions tagged [array-manipulation]

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

508 questions
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### 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 ...
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### 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 ...
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### 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 ...
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### 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, ...
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### 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 ...
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### 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: ...
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### Un-Merge a List

Introduction Most of you are familiar with the merge sort algorithm for sorting a list of numbers. As part of the algorithm, one writes a helper function called ...
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### Identifying Sequences for Cellular Automata

Background For the purposes of this challenge, an n-state cellular automaton is simply a binary function f that takes two ...
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### Bookkeeping for the Sex Bob-ombs (check if a running sum ever gets too low)

Believe it or not, the Sex Bob-ombs have become a world famous band and are currently on world tour! As their bookkeeper you must oversee their day to day finances and provide regular reports. Every ...
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### Home on the Range of Lists

This challenge is simply to return a list of lists of integers, similar to the Python range function, except that each successive number must be that deep in lists. Rules: Create a program or a non-...
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Introduction I want to build a ladder. For this, I have scavenged from the junkyard two long boards with holes in them, and I want to place the steps into these holes. However, the holes are not ...
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### Paeth-transform arrays

One of the key parts of PNG's compression algorithm is the Paeth transformation, which transforms the image in a way that makes it compress better (usually). In this challenge, your task is to write a ...
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### Almost Lexicographical List Comparison

Input Two lists A and B of nonnegative integers. Output Either 1, ...
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### 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 ...
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### Print a Block-Diagonal Matrix

Here is a simple, bite-sized (byte-sized?) code golf: given a non-empty list of positive integers less than 10, print a block-diagonal matrix, where the list specifies the size of the blocks, in order....
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### Array combinatoric comparison

Introduction You may remember sudoku, where there can only be one of each number in each row, column and block of nine. The general idea is that if the array contains but one element, you can submit ...
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### Random Golf of the Day #1: Shuffle an Array

About the Series I will be running a little series of code-golf challenges revolving around the theme of randomness. This will basically be a 9-Hole Golf Course, but spread out over several questions....
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### Complexity-free Kolmogorov(-Smirnov)

In statistics, sometimes it's useful to know whether two data samples come from the same underlying distribution. One way to do this is to use the two-sample Kolmogorov-Smirnov test. Your task will ...
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### Ordering an array of negatives, zero and positives integers with one iteration

Take an array of integers containing negative numbers, positive numbers and zeros. Group it with one iteration and in place such that all of the negative numbers come first, followed by all of the ...
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### Into how many pieces can you cut this string?

Consider a piece of string (as in "rope", not as in "a bunch of characters"), which is folded back and forth on the real line. We can describe the shape of the string with a list of points it passes ...
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### Score a game of Kingdom Builder

I want to try a new form of code golf here. Similar to bonuses, not all parts of the challenge have to be completed, but each answer has to implement a subset of certain size (and there is a core that ...
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### 0-1 Maximal Phase Counter

Consider an array of bits, say 1 1 1 0 0 0 0 1 0 0 1 0 1 1 1 1 1 0 1 0 We call a contiguous subarray of length ≥ 5 a phase if at least 85% of the bits are the ...
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### Compute the Join and Meet of Partitions

Background In this challenge, a partition of a set S means a collection of nonempty subsets of S, which are mutually disjoint ...
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### Jump the Array!

Let's play a one-player game called jump the array. To play, you only need an array of integers, say a. You start at some position ...
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### Unflatten an Array

This challenge was inspired by a question on Mathematica.SE. Say you've got a nested list/array of some arbitrary structure (the lists at each level don't necessarily have the same length). For ...
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Story Long time ago Bobby created a Bitcoin wallet with 1 Satoshi (1e-8 BTC, smallest currency unit) and forgot about it. Like many others he later though "Damn, if only I invested more back then...". ...
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### At least h with at least h

Input A list of nonnegative integers. Output The largest nonnegative integer h such that at least h of the numbers in the ...
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### Shorter than a Split Second!

Challenge You task for this question is to split an input array of integers on the second occurrence of every integer in that array. Not clear enough ? Here is an example to help Input array: <...
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### Create an array with repeated numbers

Challenge Your task in this question is to write a program or a named function which takes a positive integer n (greater than 0) as input via STDIN, ARGV or ...
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### Mode (most common element) of a list

Write a snippet to calculate the mode (most common number) of a list of positive integers. For example, the mode of d = [4,3,1,0,6,1,6,4,4,0,3,1,7,7,3,4,1,1,2,8] ...
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### Shortest Code to Translate a PHP array

NOTE: This question was migrated from https://stackoverflow.com/q/27134588/1442685 PHP QUESTION Almost purely out of curiousity, how can I take an array like this: ...
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### Shortest program to split special array

Background Imagine, you have a big array A, which is mostly zeroes, but contains a short subarray B which has only strictly ...
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### Book Stack Sort

When stacking books you usually want to put the largest ones at the bottom and the smallest ones at the top. However, my latent OCD makes me feel very uneasy if I've got two books where one is shorter ...
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### Approximated (unsorted) square from a set of values [closed]

So a colleaque came with this problem lately and I want to challange you to solve the problem in the code-golf style, shortest solution in any language wins. The Problem: Given is a random set of ...
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### Create an array of unique ints in a set range [closed]

Goal: Write a piece of code that produces a array containing all integer values in a set range in random order (upper and lower bounds included). Use any language you like, but use as little built-in ...
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### Golfscript Diagonal Array

Is there a way in Golfscript to bring all of the diagonals of an array into a single array? For example, for the array [[1 2 3][4 5 6][7 8 9]] return ...
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### Generating a single string with an Oxford comma from a list

What are some clever (brief and idiomatic) approaches to taking a list of strings and returning a single properly punctuated string built from the list, with each element quoted. This came up for me ...
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### Programming Praxis - Survive like Flavius Josephus [duplicate]

Here's a challenge inspired by Programming Praxis: http://programmingpraxis.com/2009/02/19/flavius-josephus/ Write a function josephus(n,m) that returns a list of n people, numbered from 0 to n-...
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### Rank a list of scores with “skips”

Given a list of scores (non-negative integers) pre-sorted from greatest to least: [ 10, 10, 6, 6, 4, 0] Assign each score an integer rank, beginning with 1 ...
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### Rotate 2D Array [duplicate]

Given an input of a 2 dimensional array of integers, rotate the array 90 degrees clockwise. It should work for rectangular arrays of all sizes and proportions. The rotated array should be printed at ...
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### Deplane! Deplane! (Or: RGBRGBRGB => RRRGGGBBB?)

Imagine bytes in memory for an RGB image--R and G and B represented by bytes in sequence. If an image is NxM then the memory layout will be M repetitions for vertical scanlines of 3*N bytes in ...
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### Stack the deck!

Alice and Bob like to play a card game, with a deck of cards numbered with consecutive nonnegative integers. Alice has a very particular way of shuffling the deck, though. First, she takes the top ...
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Terms A worm is any list of nonnegative integers, and its rightmost (i.e., last) element is called the head. If the head is not 0, the worm has an active segment consisting of the longest contiguous ...
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### Rotate An Integer Array with an O(n) algorithm [closed]

Write a function that rotates an integer array by a given number k. k elements from the end should move to the beginning of array, and all other elements should move to right to make the space. The ...
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### How many times is rectangular array A embedded in rectangular array B?

Given two rectangular arrays, A and B, let's say that A is embedded in B if A can be obtained from B by deleting some (or none) of the rows and columns of B. Write a program with the following I/O: ...
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### Change the innermost element type of a jagged array — any .NET language: C#, F#, VB.NET, MSIL, C++/CLI, etc

Write a class containing a method with the signature System.Array ChangeElementType(System.Array jaggedArray) (you may rename identifiers ...
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### Convert JSON string to Key / Value Arrays

Convert JSON (key/value pairs) to two native arrays, one array of keys and another of values, in your language. ...
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### Javascript: Create a 10x10 array of 1s

Obviously this challenge would be trivial with separate functions and libraries, so they aren't allowed. Your code must conform to an ECMAscript specification (any spec will do), so no browser-...