# Questions tagged [array-manipulation]

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

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### Highest cardinality grouping of contiguous integers with minimum-sum threshold

Challenge Given an array of positive integers and a threshold, the algorithm should output a set of consecutive-element-groupings (subarrays) such that each group/subarray has a sum greater than the ...
699 views

Guidelines Task Write a function that takes in a sentence (a string, or list of characters) and reverses all the words that are greater than or equal to 5 in length. Examples ...
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### Enumerate Derangements

Given some positive integer $n$ generate all derangements of $n$ objects. Details A derangement is a permutation with no fixed point. (This means in every derangement number $i$ cannot be in ...
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### 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.) ...
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### Return the nth element of an array even if its out of bound [closed]

The challenge Write a function that returns the nth element of an array even if its out of bound. ...
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### Rotate a column

Given an integer k and either a block of text, or a 2d array that the inner arrays may have unequal lengths (that resembles a block of text), rotate every character or element in the k-th column up or ...
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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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### There's an echo in my array… echo in my array… my array

Help! I seem to have an annoying echo in some of my arrays, and I'd like to get rid of it. When this occurs, the original array repeats itself somewhere in the middle causing the values to be added ...
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### Enumerate an array, grouping duplicates

The objective of this challenge is to take an array of positive integers, and enumerate its indices, grouping like elements. An enumeration without any duplicates is done by just outputting an array ...
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### Shortest power set implementation

Problem definition Print out the powerset of a given set. For example: [1, 2, 3] => [[], [1], [2], [3], [1, 2], [1, 3], [2, 3], [1, 2, 3]] Each element is to ...
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### Chunk + Enumerate a list of digits

I have a list of decimal digits: 4, 4, 4, 7, 7, 9, 9, 9, 9, 2, 2, 2, 4, 4 The list of decimal digits are known as items. We can form "chunks" from these items by ...
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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 ...
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### Circle intersection area

Description : Given x and y positions of two circles along with their radii, output the ...
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### The Lucky House

There's a minigame in Super Mario 3D World known as the Lucky House. It consists of a slot machine with 4 blocks. Each block may be one of 5 different icons (Flower, Leaf, Bell, Cherry or Boomerang) ...
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### Crossing sequences

Crossing Sequences Given a list of positive integers A, call it an increasing sequence if each element is greater than or equal to the previous one; and call it a ...
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### Output a string's cumulative slope

Challenge Given a string such as Hello World!, break it down into its character values: ...
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### An array battle with odd secret powers

Here is a relatively simple two dimensional array challenge. Imagine a battlefield of 625 foot soldiers. You command the odd troops, but unfortunately the strength of the even troops overwhelms you. ...
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### 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 ...
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### Elimination ordering

Your task is to remove smallest amount elements from a list, so the most elements are on their corresponding place. The element is on it's corresponding place, when it's value is equal to it's ...
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### 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, ...
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### Yahtzee Small Straight Detection

In the game Yahtzee, players roll five six-sided dice, and attempt to create certain hands to score points. One such hand is a small straight: four consecutive numbers, not necessarily in order. The ...
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### Dropsort with a Twist

This is my first attempt at a Code Golf question. If it needs obvious edits, please feel free to make them. Below is a description of the basic Dropsort algorithm. Dropsort is run on a list of ...
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### Skip like a rabbit!

Given a list of non-negative integers in any reasonable format, iterate over it, skipping as many elements as every integer you step on says. Here is a worked example: ...
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### Tell me how to flop

As computer scientists, you're probably all familiar with the basic list operations of pop and push. These are simple operations that modify a list of elements. However, have you ever heard of the ...
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### Golf range minimum queries of a list [closed]

(Inspired by the first problem solved in Stanford’s advanced data structures course.) Despite the academicese-heavy name, the problem we're going to solve is almost unbearably simple. We have a list ...
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### Boustrophedonise

Related but very different. A boustrophedon is a text where every other line of writing is flipped or reversed, with reversed letters. In this challenge, we will just reverse every other line, but ...
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### Matchmaker, Matchmaker, make me a match

(we won't be finding a Find or catching a tryCatch, though) This is part two of a multi-part series of implementing some ...
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### Fivenum and a little bit

(a paradox, a paradox, a most ingenious paradox) This is the first part of a multipart series inspired by different R functions. The Task Given a dataset $D$ of positive integers, I need you to ...
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### Flatten the Array!

In this challenge, your task is to create a program which takes in a nested array and returns a single-dimensional flattened array. For Example [10,20,[30,[40]],50] ...
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### 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 ...
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### 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 ...
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### Distributing parliament seats

Introduction In a general election, one would like to calculate a constant price per parliament seat. This means that for N >= 0 seats to be distributed and a ...
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### Block-sorting rows and columns in a 2D array

Given a 2D array of integers, let's sort its rows and columns in blocks. This means that you only have to sort a given row or column, but applying the transformations needed for sorting it to every ...
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### Find the largest number n positions away from n

A sequel to this question. Task Given an array of positive integers, find the largest element k for which: There exists some positive integer distance n, so that the element in the array located ...
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### 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 ...
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### Weapons of Math Instruction

Last time when I tried to come up with something easy that wasn't a duplicate, it ended up being way too hard.. So hopefully this time it's indeed something newcomers can try as well. Input: An ...
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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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### Find longest consecutive characters in 2D array

Challenge Given a 2D array, find the length and direction of all the longest consecutive characters. If there are ties, output every possible winning combination in any order, (winners can overlap ...
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### Split into three!

Given a string, you've to split it into groups of three characters (by padding _ at the end). Related, but still it's different. Sample I/O: ...
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### Incremental Ranges!

Your task is to, given two positive integers, $x$ and $n$, return the first $x$ numbers in the incremental ranges sequence. The incremental range sequence first generates a range from one to \\$...
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### Extract Local Maxima

Given an array of positive integers, output an array of all the elements that are greater than or equal to the adjacent ones. Most elements will have two adjacent elements; the first and last element ...
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### Parity of sum of other elements

Task Given an array of positive integers, replace each element with the parity of the sum of the other elements. The array is guaranteed to have at least 2 elements. Definition Parity: whether a ...
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### Make an inversedict

Input A dictionary with string keys and string values. Output The 'inversedict' of this dictionary. How to make an inversedict An inversedict is a dictionary with string keys and string array ...
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### Is this a submatrix?

This is the 2-dimensional generalisation of this challenge. For our purposes, one matrix (or 2D array) A is considered a submatrix of another matrix B, if A can be obtained by completely removing a ...
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### Smallest groups in an array

Introduction Let's observe the following array: [1, 1, 1, 2, 2, 1, 1, 1, 1, 2, 2, 2, 1, 1, 1] A group consists of the same digits next to each other. In 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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### Implementing a stack

I can't believe we don't have this already.. It's one of the most important data-structures in programming, yet still simple enough to implement it in a code-golf: Challenge Your task is to ...
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### Maximum summed sub sequences with no two numbers sharing the same digit [closed]

Suppose there are 5 positive integers in an array or list as 14, 12, 23, 45, 39. 14 and 12 cannot be taken in the subset as 1 is common in both. Similarly {12, 23}, {23, 39}, {14, 45} cannot be ...