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Questions tagged [integer]

For challenges involving the manipulation of integers.

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18 votes
26 answers
2k views

Is it a tetrate of two?

The tetration operation consists of repeated exponentiation, and it is written ↑↑. For instance, 3↑↑3 =3 ^(3^3) = 3^27 = 7,625,597,484,987 A tetrate of two is an ...
43 votes
92 answers
5k views

Output the missing integer

You will be given a string. It will contain 9 unique integers from 0-9. You must return the missing integer. The string will look like this: ...
24 votes
30 answers
3k views

A bit of a digital XOR

Here are the first 100 numbers of a sequence: ...
26 votes
23 answers
2k views

Reconstruct an arithmetic sequence

Given a finite arithmetic sequence of positive integers with some terms removed from the middle, reconstruct the whole sequence. The task Consider an arithmetic sequence: a list of positive integers ...
17 votes
21 answers
2k views

Divmod continuously until the remainder is 1 or 0, then get the remainder

The task is simple, divide, get the quotient and the remainder, and if the remainder isn't 1 or 0, do the same thing (quotient divmod remainder) until the remainder is 1 or 0, then get the remainder. ...
11 votes
23 answers
888 views

Construct a uInt from an array of bits

Task is simple! Take an array of binary values (can be boolean, 0/1, etc.) and use those bits to construct an n-th bit long unsigned integer (return type does not need to be an unsigned integer, just ...
36 votes
46 answers
5k views

Half, Half Half, and, Half

Consider the following number sequence: \$ 0, \frac{1}{2}, \frac{1}{4}, \frac{3}{4}, \frac{1}{8}, \frac{3}{8}, \frac{5}{8}, \frac{7}{8}, \frac{1}{16}, \frac{3}{16}, \frac{5}{16}, \frac{7}{16}, \...
13 votes
17 answers
1k views

A Fine sequence with fine interpretations

The ubiquitous Catalan numbers \$C_n\$ count the number of Dyck paths, sequences of up-steps and down-steps of length \$2n\$ that start and end on a horizontal line and never go below said line. Many ...
29 votes
46 answers
4k views

Which Card is it?

Introduction Long ago, when I used to code card games with usual playing cards, I used to specify a number for each card and call a function with some number to get a card. This somewhat inspired me ...
17 votes
45 answers
3k views

The inverse Collatz Conjecture

I think the Collatz Conjecture is already well-known. But what if we invert the rules? Start with an integer n >= 1. Repeat the following steps: If n is even, multiply it by 3 and add 1. If n is ...
36 votes
41 answers
4k views

Is it a Mersenne Prime?

A number is a Mersenne Prime if it is both prime and can be written in the form 2n-1, where n is a positive integer. Your task is to, given any positive integer, determine whether or not it is a ...
29 votes
37 answers
2k views

Where are Champernowne's zeroes?

Consider the infinite string of all nonnegative decimal integers concatenated together in order (akin to Champernowne's constant): ...
39 votes
28 answers
2k views

Sum the powers that be

A simple but hopefully not quite trivial challenge: Write a program or function that adds up the kth powers dividing a number n....
4 votes
1 answer
596 views

Which line is best?

Consider an \$n \times n\$ grid of integers. The task is to draw a straight line across the grid so that the part that includes the top left corner sums to the largest number possible. Here is a ...
15 votes
24 answers
5k views

FizzFizzFizzBuzz!

Given a positive integer n, output the "FizzFizzFizzBuzz" sequence for that number: print the decimal representations of the numbers 1 through ...
14 votes
14 answers
2k views

Break an integer into even- and odd-indexed bits

Objective Given an integer \$n\$ interpreted as two's complement binary, output two integers, namely the integer consisting of \$n\$'s bits at places of \$2^0, 2^2, 2^4, \cdots\$, and the integer ...
26 votes
57 answers
4k views

Converting Strings to Decimals (Gone Wrong)

What? Many programming languages, both practical and esoteric, have functions, methods, etc to convert a given string to a decimal number. This is how the process might work: For each character in ...
41 votes
81 answers
5k views

As Easy as One-Two-Three

Write a program or function that takes in a positive integer. You can assume the input is valid and may take it as a string. If the number is any of ...
18 votes
13 answers
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, ...
14 votes
7 answers
2k views

How quickly can you type this unary string?

If I want to type the string aaa, the least keystrokes I can type it in is 3: a a a. But if I want to type the string ...
26 votes
44 answers
3k views

X Steps Forward, 1 Step Back

Here the first 100 numbers of an easy sequence: ...
7 votes
16 answers
1k views

Emoticon numbers!

(related) Your challenge is to output the highest number you can. You can output as a number or as a string. You must output something that matches the regex ^\d+$,...
55 votes
160 answers
10k views

Stay away from zero

Task Given a non-negative integer n, output 1 if n is 0,...
26 votes
26 answers
3k views

How far from binary?

Given a decimal integer n as input, output the smallest (in terms of absolute value) decimal integer m such that the absolute ...
18 votes
39 answers
2k views

Rudin-Shapiro sequence

The Rudin-Shapiro sequence is a sequence of \$1\$s and \$-1\$s defined as follows: \$r_n = (-1)^{u_n}\$, where \$u_n\$ is the number of occurrences of (possibly overlapping) \$11\$ in the binary ...
26 votes
32 answers
2k views

Let's design a digit mosaic

Challenge Given a positive integer \$N\$, repeat each of its digits \$d_1, d_2, d_3, \cdots, d_n\$ a number of times corresponding to its position in \$N\$. In other words, each digit \$d_k\$ should ...
83 votes
193 answers
10k views

Output the sign

Given a number N, output the sign of N: If N is positive, output 1 If N is negative, output -1 If N is 0, output 0 N will be an integer within the representable range of integers in your chosen ...
2 votes
3 answers
198 views

Rank poker High Card hands [closed]

In the poker game there are 1277 unique 'High Card' ranks. It's 1287 (13 over 5) if we include all straights. The challenge is to write a function which returns an integer value corresponding to the ...
67 votes
165 answers
11k views

Print all integers

Write a program or function which will provably print all integers exactly once given infinite time and memory. Possible outputs could be: ...
10 votes
5 answers
958 views

Manipulate integers to zero

Objective Given a nonempty unordered list of positive integers, decide whether they can be added, negated, or multiplied to yield a single zero. Each given number must be used exactly once. There is a ...
5 votes
16 answers
3k views

Move my liquid to make me equal

You are given 4 positive integers: volume of the first container (v1), volume of the second container (v2), volume of the liquid ...
26 votes
27 answers
2k views

Complete a sequence using its distances

Given \$A = (a_1,\dots,a_k)\ k\ge2 \$ a sequence of positive integers, in which all elements are different. Starting from \$i=2\$, while \$a_i\in A:\$ (until the last element) If \$d=|a_i-a_{i-1}|\$ ...
39 votes
67 answers
4k views

Is this a Permutation of 1..n

Input a non-empty array with \$n\$ positive integers. Test if the input array contains every integer in \$1\cdots n\$. In case you prefer 0-indexed numbers, you may choose to input an array of non-...
26 votes
19 answers
2k views

Find Recursively Prime Primes

The Recursively Prime Primes is are sequence of primes such that p(1) = 2 p(n) = the p(n-1)th prime Here is an example of how one might calculate the 4th ...
34 votes
90 answers
7k views

iHateOddNumbers

Task Given a non-negative number, check if it's odd or even. In case it's even, output that number. Otherwise, throw any exception/error that your language supports, and stop the program. Example with ...
43 votes
46 answers
4k views

An Array of Challenges #1: Alternating Arrays

Alternating Arrays An alternating array is a list of any length in which two (not necessarily different) values are alternating. That is to say, all even-indexed items are equal, and all odd-indexed ...
35 votes
28 answers
8k views

Could you please stop shuffling the deck and play already?

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 list ...
23 votes
23 answers
3k views

Longest Zero Sum Sub-array

Given an array of integers. Find out its longest sub-array (contiguous subsequence) whose sum is 0. The sub-array for output may be an empty array. Input Input an array of integers. Output Output the ...
51 votes
41 answers
3k views

Moving modest minimum

Inspired by a question over at Stack Overflow. The title here is entirely my fault. The challenge Given a list of positive integers containing at least two entries, replace each number by the ...
20 votes
31 answers
2k views

Binary Countdown Length

inspired by Count down from infinity Given a non-negative integer N, output the number of repetitions of the following steps it takes to reach 0: Convert ...
33 votes
68 answers
6k views

Integer Lists of Noah

Introduction: I think we've all heard of it, but here a very brief summary: Noah gathered two of every species of animal on the planet, male and female, to save in his Ark during a great flood. The ...
11 votes
30 answers
1k views

Multiplicative undelta

Let us define the "multiplicative deltas" of values \$[\; a_0, \cdots a_N, \;]\$ as: $$ [\; a_1 / a_0, \cdots, a_{i+1} / a_i, \cdots, a_N / a_{N-1} \;] $$ The reverse operation - namely "...
10 votes
12 answers
1k views

Counting Collinear Points

Given two points \$(x_1, y_1)\$ and \$(x_2, y_2)\$ with integer coordinates, calculate the number of integer points (excluding the given points) that lie on the straight line segment joining these two ...
25 votes
27 answers
2k views

Sort by Largest Digit(s)

Challenge: Given a list of integer, sort descending by their single largest digit(s). The order for numbers with the same largest digit are then sorted by second largest digit, etc. We ignore ...
23 votes
31 answers
3k views

Is this a powerful number?

A powerful number is a positive integer \$n\$ such that for every prime \$p\$ that divides \$n\$, \$p^2\$ also divides \$n\$. Or equivalently, \$n\$ is powerful if and only if it can be written in the ...
22 votes
21 answers
3k views

Fibonacci Encoding

Fibonacci coding is a universal code, which can encode positive integers of any size in an unambiguous stream of bits. To encode an integer \$ n \$: Find the largest Fibonacci number less than or ...
29 votes
30 answers
4k views

Inverse Colombian Function

Let's define a sequence: The n digit summing sequence (n-DSS) is a sequence that starts with n. If the last number was k, then the next number is k + digit-sum(k). Here are the first few n-DSS: ...
27 votes
37 answers
3k views

Triangular Dependencies

A triangular number is a number that is the sum of n natural numbers from 1 to n. For example ...
23 votes
36 answers
2k views

Smallest Bit Rotation

For a given positive integer, try to find out the smallest possible rotation resulted by rotating it 0 or more bits. For example, when the given number is 177, whose binary representation is \$...
17 votes
23 answers
2k views

Monotone sequence beatitude

Provided that the input is a monotone sequence of three or more integers: Output -2 if the sequence strictly decreases. Example: [7,4,3,2] Output -1 if the ...

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