# Questions tagged [array]

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

814 questions
Filter by
Sorted by
Tagged with
1k views

• 41.6k
2k views

### Weave two lists, cycling if necessary

Consider two lists, A and B. To weave them together, we take the first element of A, then the first element of B, then the next element of A, the next element of B, and so on, ending with the last ...
• 38.8k
2k views

### Emulate Jelly's tie-scan

The golfing language Jelly has a built-in ƭ called "tie", that cycles through a list of functions every time it's called. For example, ...
• 41.6k
1 vote
125 views

### Interlaced array [duplicate]

You are given an array A of length N and an array B of length ...
1k views

### Reconstruct a list of strings from its prefixes

emanresu A posted a challenge to reconstruct an ordered list of integers from its unordered set of unordered prefixes. Many users (beginning with xnor's answer) noticed that summing each unordered ...
• 15.9k
1k views

### Reconstruct a list from its prefixes

A list $[a_1,a_2,a_3 \cdots a_n]$ can be uniquely represented as an unordered list of its prefixes - $[[a_1],[a_1, a_2], [a_1,a_2,a_3] \cdots [a_1,a_2,a_3 \cdots a_n]]$. This can be in any order ...
• 41.6k
1k views

### Contract a tensor

Introduction Tensor contraction is an operation that can be performed on a tensor. It is a generalization of the idea of the trace of a matrix. For example, if we have a rank-2 tensor (a matrix) and ...
• 2,123
2k views

### Search the deepest depths of an array

Given a ragged array, find the length of the largest subarray that contains the depth of that subarray. The base array layer has a depth of 0. Here is an example: ...
• 4,219
2k views

### Remove falsy rows and columns

Your challenge is to, given a matrix of nonnegative integers, remove all rows and columns that contain a 0. For example, with this matrix: ...
• 41.6k
2k views

### What and where is the max?

This small challenge derives from my annoyance at discovering that numpy doesn't have a built in function for it. Input An n by m matrix of integers. Output The maximum value in the matrix and the 2d ...
• 3,153
403 views

### Busy Letters & Evil CEOs

Imagine you are given an array/string containing $5$ letters of the English alphabet, with each letter having any value from A to Z (inclusive). Every day, each letter will perform a job, which can ...
• 487
3k views

### "Perfect" an array

Given an n non-negative integers, how many numbers must be changed so that each number x appears x times? You cannot add or remove elements, only replace them with other numbers. For example: ...
• 4,219
955 views

### Unnecessary Fluff

Following the great advice (what do you mean it's not advice?!) on Adding unnecessary fluff we can devise the following task: Take a list of positive integers and a positive integer $m$ as input. ...
• 10.6k
248 views

### Is it stuck in a counting loop? [duplicate]

Given a list of non-negative integers the function $f$ replaces every integer with the number of identical integers preceding it (not necessarily contiguously). So ...
• 99.6k
1k views

### Night hike partitioning

We want to go on a night hike with the youth group, but of course not everyone has their torch, even though we told them we planned to split up. What options are there for group formation if n teens ...
• 2,660
967 views

### One-dimensional map colouring

It is a well-known fact that you can colour a two-dimensional map with four colours in such a way that two countries with a common border always have different colours. There have already been enough ...
• 2,660
3k views

### Just another traffic jam!

One lane is closed, the vehicles have to thread their way in according to the zip-lock system: One car from one lane, the next car from the other lane, always taking turns. Input: Two vehicle queues, ...
• 2,660
4k views

### Which skill to train?

Story (skip, if you prefer the naked task): You need five skills for an imaginary sport: Speed, strength, endurance, accuracy and tactics. If you achieve a score in each of these disciplines, you can ...
• 2,660
324 views

### How many twisted corners?

Your challenge is to output the number of twisted corners given a 2x2 Rubik's Cube scramble. For the purpose of this challenge, twisted corners are defined as corners where the colour of the top/...
• 9,438
2k views

### Seat gangs as far as possible

Imagine there are $n$ people $\{a_1, a_2, \ldots, a_n\}$ who enter a room in order and sit down in $n$ seats, arranged in a row. Each of these people belong to some gang, indicated by an integer ...
• 7,131
4k views

### How many umbrellas to cover the beach?

You work at a beach. In the afternoon, the sun gets quite hot and beachgoers want to be shaded. So you put out umbrellas. When you put out umbrellas you want to shade the entire beach, with as few ...
• 99.6k
1k views

### Transpose a multidimensional array

Transposition is an operation on 2-dimensional arrays that flips every element across the main diagonal: ...
• 41.6k
851 views

### Output the longest list

In this challenge you will take a non-empty (finite) list of (possibly infinite) lists of positive integers, and your task is to output the longest one. An infinite list is longer than a finite list ...
• 99.6k
2k views

### Complement an infinite list

In this challenge, we define the complement of a list of positive integers as all positive integers not included in that list. For example, the complement of the even numbers ...
• 41.6k
1 vote
562 views

• 10.4k
666 views

### Complete the landscape

Carcassonne is a tile-based game, where the objective is to construct Roads, Cities and Monasteries, in order to score points. The game works by players taking turns to draw and place tiles to ...
• 50.1k
1k views

Given a list, L, of sets of numbers like this: [[1], [0,2,3], [3,1], [1,2,3]] Output a single list of numbers such that 2 ...
• 13k
2k views

### Compute cumulative means efficiently

Consider a sorted array of positive floating point numbers such as: input = [0.22, 2.88, 6.35, 7.17, 9.15] For each integer $i$ from 1 up to the last value in ...
• 3,153
933 views

### "Signpost" puzzle from Tatham's collection

Simplified version of "Signpost" puzzle from Simon Tatham's Portable Puzzle Collection. How the puzzle is created We pick up randomly positive integer N ...
• 3,423
1k views

Background Being in a philosophical mood, I remembered one old idea. I think it is suitable for CG. Duplicates are not found, but it's of course just a kind of totalistic cellular automaton or erosion....
• 3,423
3k views

### The Jaccard Index

The Jaccard index / similarity coefficient, also known as the Tanimoto index / coefficient, is a statistic used for gauging the similarity and diversity of finite sample sets. It was developed by ...
• 1,597
2k views

• 99.6k
3k views

### Is it a valid chemical?

Non-metals typically* have a fixed number of covalent bonds in every chemical they are part of. Given the number of bonds every element requires, output whether it's possible to construct a single ...
• 13k
3k views

### Is it traversable?

Imagine that a list of integers describes the heights of some two-dimensional terrain as seen from the side. Stamina: [ 4 4 4 4 4 4 3 3 3 3 2 2 2 - ] O ...
• 26.3k
814 views

### Guessing on straws

Dedicated to Martin Gardner, taken from his book Background In the old days, the Slavs had a divination method for finding out whether a girl would get married. The girl would clutch six straws in her ...
• 3,423
3k views

### Counting Letters in a String

Write a program or function that takes in a string and outputs a count of each modern English alphabet letter in the string, case-insensitive. Input: A string consisting of printable ASCII characters (...
• 1,802
626 views

### String with the smallest sum of ASCII values

Description In this challenge, you need to write a function that takes in a list of strings and returns the smallest string based on their ASCII value. You should assume that the input list contains ...
• 1,802
634 views

### Voronoi-Lloyd ASCII art [closed]

Voronoi diagram is a partition of a plane (or part of plane) into regions close to each of a given set of objects ("seeds"). Here we’ll be dealing with discrete arrays or even rather with ...
• 3,423