Questions related to elementary arithmetic.

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2answers
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Restricted average (arithmetic mean) – i.e. without obvious built-ins [closed]

Introduction The arithmetic mean is defined as being equal to the sum of the numerical values of each and every observation divided by the total number of observations. Symbolically, if we have a ...
6
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6answers
171 views

Find how many pair elements sums up to N [closed]

Based on a recent question in StackOverflow Write a program/function that takes in one ARRAY/list and returns the number of pair-values which sums up to a given TOTAL. Explaining TOTAL=4, ...
40
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27answers
3k views

How many steps does it take from n to 1 by subtracting the greatest divisor?

Inspired by this question over at Mathematics. The Problem Let n be a natural number ≥ 2. Take the biggest divisor of n – which is different from n itself – and subtract it from n. Repeat until ...
4
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6answers
412 views

Traveling on a flat Earth

Coordinates in the flat-Earth world consist of latitude (x) and longitude (y), which are integers in the range 0...9999. Much like Gaussian integers, but they are always written using this notation: ...
14
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15answers
907 views

Find the n-th perfect power!

A perfect power is a number of the form a**b, where a>0 and b>1. For example, 125 is a perfect power because it can be expressed as 5**3. Goal Your task is to write a program/function that ...
6
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15answers
294 views

Find the positive divisors!

Definition A number is positive if it is greater than zero. A number (A) is the divisor of another number (B) if A can divide B with no remainder. For example, 2 is a divisor of 6 because 2 can ...
30
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33answers
2k views

Compute the Adler-32 checksum

Background Adler-32 is a 32-bit checksum invented by Mark Adler in 1995 which is part of the widely used zlib library (also developed by Adler). Adler-32 is not as reliable as a 32-bit cyclic ...
8
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7answers
267 views

Find the repetend of the decimal representation!

In this challenge 2 years ago, we found the period of a unit fraction (1/n where n is a natural number). Now, your task is to write a program/function to find the repetend of a unit fraction. The ...
8
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6answers
417 views

Calculate the Kronecker sum of two matrices

In the examples below, A and B will be 2-by-2 matrices, and the matrices are one-indexed. A Kronecker product has the following properties: A⊗B = A(1,1)*B A(1,2)*B A(2,1)*B A(2,2)*B ...
8
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3answers
272 views

One-to-one correspondence between pairs of integers and the positive integers

It is well-known that there are one-to-one correspondences between pairs of integers and the positive integers. Your task is to write code defining such a correspondence (by defining a pair of ...
8
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8answers
331 views

m-nomial coefficient

While binomial coefficient is the coefficient of (1+x)**n, m-nomial coefficient is the coefficient of (1+x+x**2+...+x**(m-1))**n. For example, m(3,5,6) is the coefficient of x**6 in the expansion of ...
7
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9answers
601 views

How many minimum days will he take to complete N units of work?

A person has to complete N units of work; the nature of work is the same. In order to get the hang of the work, he completes only one unit of work in the first day. He wishes to celebrate the ...
15
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33answers
2k views

Sum the odd square numbers less than N

Write a program or function to output the sum of the odd square numbers (OEIS #A016754) less than an input n. The first 44 numbers in the sequence are: 1, 9, 25, 49, 81, 121, 169, 225, 289, 361, ...
6
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2answers
276 views

Federal income tax calculator for procrastinators

Today is Tax Day! Oops. Well, today is tax day if you are a resident of Maine or Massachusetts. So you're probably still completing your return and need a calculator for when you get to Line 44. ...
10
votes
7answers
389 views

Convert to Roman Numeral!

Your task is to convert a given positive integer from Arabic numeral to Roman numeral. Things get difficult when you count to 4000. The romans did this by adding a line above a symbol to multiply ...
20
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14answers
871 views

Generate the minimal remainder sequence

Every number can be represented using an infinitely long remainder sequence. For example, if we take the number 7, and perform 7mod2, then 7mod3, then 7mod4, and so on, we get ...
2
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3answers
248 views

Solve a quadratic equation using Vieta's formulas

Exposition Your mathematics teacher is a big fan of Vieta's formulas, and he believes that you should use them to solve quadratic equations. Given the equation ax^2 + bx + c = 0 the product of its ...
23
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36answers
2k views

Greatest Common Divisor

Your task is to compute the greatest common divisor (GCD) of two given integers in as few bytes of code as possible. You may write a program or function, taking input and returning output via any of ...
21
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25answers
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The plus-minus sequence

The plus-minus sequence The plus-minus sequence is one that starts with two seeds, a(0) and b(0). Each iteration of this sequence is the addition and subtraction of the previous two members of the ...
27
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14answers
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The Arithmetic Derivative

The derivative of a function is a cornerstone of mathematics, engineering, physics, biology, chemistry, and a large number of other sciences as well. Today we're going to be calculating something only ...
13
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8answers
752 views

Express a number with only 0-9 and the four operations

Explanation Befunge is a two-dimensional program that uses stacks. That means, to do 5 + 6, you write 56+, meaning: 56+ 5 push 5 into stack 6 push 6 into stack + pop the first two items in ...
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20answers
290 views

Print the sum of the squares of some numbers

This is a little codegolf challenge from codingame.com. I was wondering how much Python3 code is necessary (but of course answers are not limited to Python3). Input The first line contains one ...
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6answers
2k views

X+Y=Z - but in which base?

The Challenge Given 3 numbers X, Y and Z in base B, find a B in which the addition of X and Y yields Z. The inputs x = 2 0, Y = 1 2 and Z = 3 2 could yield 5 because 2 0 + 1 2 = 3 2 in base 5. You ...
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13answers
2k views

A curious prime fraction formula

Given a positive integer n output the integers a and b (forming reduced fraction a/b) such that: Where pk is the k th prime number (with p1 = 2). Examples: 1 -> 3, 5 2 -> 12, 25 3 -> 144, ...
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9answers
4k views

Addition in base -1+i

Gaussian integers are complex numbers of the form a+bi where a and b are both integers. In base -1+i, all Gaussian integers can be uniquely represented using the digits 0 and 1, without the need for a ...
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37answers
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Happy Rounded Pi Day

To celebrate Rounded Pi Day, you must take advantage of today's date to make a program that takes in a circle's diameter and outputs its circumference by multiplying the diameter by 3.1416, where ...
13
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11answers
589 views

Minimum Scalar Product

Minimum Scalar Product The inspiration for this code golf problem is from Google's code jam competition. The premise behind the problem is, given the input of two vectors of varying lengths, find the ...
18
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12answers
2k views

Calculate the volume of an object

You can determine the volume of objects based on a given set of dimensions: The volume of a sphere can be determined using a single number, the radius (r) The volume of a cylinder can be determined ...
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4answers
168 views

Solve an algebraic expression

The Challenge Your task is to create a program that can solve an algebraic equation. Input Input will consist of a String. The string will be an equality involving the variable x, and follows the ...
18
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16answers
2k views

Center of Mass from a list of coordinates and their masses

Here is a quick Monday morning challenge... Write a function or program in the least number of bytes that: Takes as input a list of [x,y] coordinates Takes as input a list of the [x,y] coordinates' ...
24
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5answers
921 views

Write a Morse Calculator

Write a program or function that takes a mathematical expression in Morse code as input, and returns the solution in Morse code. Valid operations are plus: + and minus: _ (underscore). You can assume ...
20
votes
9answers
846 views

Highly composite numbers

A highly composite number is a positive integer that has more divisors than any smaller positive integer has. This is OEIS sequence A002182. Its first 20 terms are 1, 2, 4, 6, 12, 24, 36, 48, 60, ...
27
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12answers
2k views

One-zero dividend

Challenge description For every positive integer n there exists a number having the form of 111...10...000 that is divisible by n i.e. a decimal number that starts with all 1's and ends with all 0's. ...
13
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6answers
463 views

Find the optimal sliding door width

Sliding doors have varying prices based on the width of the doors. The different prices are as follows: 60 - 80 cm: ¤150 81 - 100 cm: ¤200 101 - 120 cm: ¤220 When buying a closet you would ...
11
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54answers
4k views

Golf the xᵗʰ root of x

While bored in high-school (when I was half my current age...), I found that f(x) = x(x-1) had some interesting properties, including e.g. that the maximum f for 0 ≤ x is f(e), and that the binding ...
37
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39answers
3k views

Print N Squared

Write a program or function that takes in a non-negative integer N from stdin or as a function argument. It must print or return a string of a hollow ASCII-art square whose sides are each made with N ...
8
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4answers
373 views

How drunk am I and when can I drive again?

It's weekend and what are the cool guys doing on weekends? Drinking of course! But you know what's not so cool? Drinking and driving. So you decide to write a program that tells you how loaded you are ...
11
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15answers
304 views

Congruence Relations

Given 3 positive integers a, b, and n (whose maximum values are the maximum representable integer value in your language), output a truthy value if a ≡ b (mod n), and falsey otherwise. For those ...
15
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3answers
311 views

Arbitrary Precision Integer Division

We will be implementing division for arbitrarily large integers. This is code-golf. The task is to write a program or function that implements arbitrary precision integers and Division on them. ...
12
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4answers
185 views

Help recalculate your rep!

A couple months ago, we had a discussion on meta about increasing the reputation awarded for upvotes on questions. Here's the basics of our current reputation system for votes:1 A question upvote U ...
13
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7answers
663 views

Recursive 2x2 determinant

The determinant of a 2 by 2 matrix a b c d is given by ad - bc. Given a matrix of digits with dimensions 2n by 2n, n ≥ 1, output the result obtained by recursively computing the determinant of ...
29
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18answers
3k views

Sort by Multiplying

You should write a program or function that given a list of positive integers multiplies each element with the smallest positive integer possible to create a strictly increasing list. For example if ...
9
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3answers
266 views

Verify the birth number

A Norwegian Birth Number consists of 11 digits, composed the following way: DDMMYYiiikk DD is the day (from 01-31) MM is the month (from 01-12) YY is the year (from 00-99). It's not differentiated ...
17
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7answers
2k views

Who's gonna win the football game?

The American football championship, Super Bowl 50, is happening today at 11:30pm UTC (and you can watch it live online). This challenge was made to celebrate it. In an American football game, two ...
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25answers
2k views

Difference of three input integers

Implement a function diff that takes as input three integers x, y, and z. It should return whether subtracting one of these numbers from another gives the third. Test cases: diff(5, 3, 2) yields True ...
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17answers
2k views

Inverse function

Wouldn't it be neat if programming functions could be inverted, just like the mathematical function they implement? Write a function (or program) that takes one input x in any form, that outputs ...
20
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34answers
3k views

Electrical outlet

This is a problem from NCPC 2005. Roy has an apartment with only one single electrical outlet, but he has a bunch of power strips. Compute the maximum number of outlets he can have using the power ...
25
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18answers
2k views

The RATS sequence

Your task is to generate the nth term of the RATS sequence, where n is the input. The RATS sequence is also known as the Reverse Add Then Sort sequence. This sequence can also be found here: ...
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26answers
2k views

Distance between two points in n-dimensional space

Here is another simple one: The Challenge Given two points in an n-dimensional space, output the distance between them, also called the Euclidean distance. The coordinates will be rational ...
21
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13answers
1k views

What's the point?

Write a program or function that takes in two integers that represent the X and Y coordinates of a point on a Cartesian plane. The input may come in any reasonable format as long as the X value comes ...