# Questions tagged [programming-challenge]

Programming challenges are off-site challenges meant to offer programmers educational experiences while testing their abilities.

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### Project Euler #3 - largest prime factor

I was going through the Project Euler problem #3 and made a program to solve it. The problem is as follows: The prime factors of 13195 are 5, 7, 13 and 29. What is the largest prime factor of the ...
5k views

### Project Euler Problem 12 - triangle number with 500 divisors

I've just done Problem 12 of Project Euler: What is the value of the first triangle number to have over five hundred divisors? The $N$'th triangle number is the sum of all natural numbers ...
4k views

### Project Euler Problem #4 - Palindromic number

The problem is as follows: A palindromic number reads the same both ways. The largest palindrome made from the product of two 2-digit numbers is 9009 = 91 × 99. Find the largest palindrome made ...
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### Efficiency of Project Euler problem 35

The number, 197, is called a circular prime because all rotations of the digits: 197, 971, and 719, are themselves prime. There are thirteen such primes below 100: 2, 3, 5, 7, 11, 13, 17, 31, 37, ...
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### Project Euler problem 1 in Python - Multiples of 3 and 5

I'd like suggestions for optimizing this brute force solution to problem 1. The algorithm currently checks every integer between 3 and 1000. I'd like to cut as many unnecessary calls to ...
2k views

### Determining winning hand in poker

After having reviewed this question, I recalled that I haven't solved Project Euler's problem 54. So I did it, however, I fount out that implementing the exact rules is rather tricky. So I ...
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### Project Euler - Problem 54: testing poker hands

This was a very fun and thought provoking problem, and I'm quite proud of the way I was able to pull it off. I broke it down into 2 parts, testing and comparing. Testing each group of cards for ...
823 views

### Matrix of articles and authors from large JSON dataset

Given the following JSON data containing 4 articles by 4 different authors: ...
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### Printing longest sequence of zeroes

I am doing a coding exercise in codility and I came across this question: A binary gap within a positive integer N is any maximal sequence of consecutive zeros that is surrounded by ones at both ...
418 views

### LeetCode 49: Group Anagrams

I'm exceeding the time limit for a 10,000 word test case provided on LeetCode: Given an array of strings, group anagrams together. For example, given: ...
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### The Beauty and the Strings

This originally appeared in Facebook's hacker cup 2013. Solving it was fun, though I find myself looping through similar data quite often. Challenge: Print the maximum beauty of strings. ...
316 views

### Calculating the number of rooms in a 2D house

I stumbled upon this problem on cses.fi (a problem set for the Finnish Olympiad in Informatics. This problem is in finnish so I'll translate it). I'll describe the problem, present the code and think ...
306 views

### Efficiently counting rooms from a floorplan

Note this was the wrong version of the code. The updated version is here: Efficiently counting rooms from a floorplan (version 2) My apologies! Update Final version 3 with test harness here: ...
384 views

### Calculating number of unharmed leaves

I recently came across this problem that asks you to print the number of leaves not eaten by the caterpillars: As we all know caterpillars love to eat leaves. Usually, a caterpillar sits on leaf, ...
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### Efficiently counting rooms from a floorplan (version 2)

This is version 2 of Efficiently counting rooms from a floorplan. I had accidentally pasted in the wrong version of the code. Update Final version (version 3) of the code with updated test harness ...
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### Project Euler #5 - Lowest common multiple of 1 through 20

This is my code. All comments welcome. Last time run it only took 335 milliseconds: ...
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### Sieve of Eratosthenes: making it quicker

I was thinking about doing problem 23 of Project Euler. It includes the difficulty where you have to factorize primes. I had already done that in problems I solved earlier, but it was only necessary ...
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Challenge: Write a program which determines the largest prime palindrome less than 1000. The answer is 929, and my program correctly finds and prints this, but actually ended up being more complex ...
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### Project Euler #7 10001st prime

I decided to start working on the Euler project exercises. I'm doing fine for now but the seventh problem is running quite slow and I can't think of anything to make it work faster. It takes around ...
3k views

### Sieve of Sundaram for Project Euler 7: Python implementation slower than C++ and R

A friend of mine recently started learning R, and she complained to me that R is very slow. She was working on Project Euler Problem 7, which asks for the value of the 10001st prime number. For ...
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### The FizzBuzz challenge in Java 8 written in a short, readable and interesting way

I decided to take on the FizzBuzz challenge with as twist that I would use Java 8 concepts to make it a bit modular, yet still let it be a short, readable and understandable program. This in contrary ...
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### 100 gunmen in circle kill next person

The question is here. 100 people are standing in a circle with gun in their hands. 1 kills 2, 3 kills 4, 5 kills 6 and so on till we are left with only one person. Who will be the last person alive....
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### DailyProgrammer 284: Wandering Fingers

Description Software like Swype and SwiftKey lets smartphone users enter text by dragging their finger over the on-screen keyboard, rather than tapping on each letter. You'll be given ...
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### Project Euler #2 (Even Fibonacci numbers) in Swift

I figured working through Project Euler problems in Swift would be a good way to learn any tips or tricks. For example, tuples are something I'm not used to using, but they proved useful here. Using ...
20k views

### Smallest Multiple

I just recently learned about Project Euler and have started doing the problems on there. I cleared problem 1 and 2, had no idea how to do 3 and 4, and started to do 5. I've seen the post regarding ...
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### Writing nested for loops to produce certain output

My task: Write nested for loops to produce the following output with each line 48 characters wide: ...
765 views

### CodeFights: Pipes game

Description Carlos always loved playing video games, especially the well-known computer game "Pipes". Today he finally decided to write his own version of the legendary game from scratch. In ...
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### Euler #3 largest prime factor

Problem Statement This problem is a programming version of Problem 3 from projecteuler.net The prime factors of 13195 are 5, 7, 13 and 29. What is the largest prime factor of a given number N?...
654 views

### 4 sum challenge (part 2)

This is a continued discussion from (4 sum challenge) by return count only. Problem Given four lists A, B, C, D of integer values, compute how many tuples (i, j, k, l) there are such that A[...
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### Project Euler “Even Fibonacci numbers” in Java 8

I'm looking for general advice on my code on the following problem: Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with 1 and 2, the first 10 ...
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### Hypothetical SalesTax challenge

I have a small solution to the following hypothetical problem: Basic sales tax is applicable at a rate of 10% on all goods, except books, food, and medical products that are exempt. Import duty ...
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### Project Euler #8

I was doing Project Euler #8, which asks: The four adjacent digits in the 1000-digit number that have the greatest product are 9 × 9 × 8 × 9 = 5832. ...
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### Find the binary gap of a number N

For example, number 9 has binary representation 1001 and contains a binary gap of length 2. The number 529 has binary representation 1000010001 and contains two binary gaps: one of length 4 and one of ...
441 views

### Count the occurence of nucleobases in DNA string

Inspired by this meta question I decided to take a look at Rosalind. Their first challenge seemed easy enough: An example of a length 21 DNA string (whose alphabet contains the symbols 'A', 'C', 'G'...
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### Largest Prime Factor redux

There have been a number of questions asking for comments on code for the Project Euler problem to compute the largest prime factor of a number. A primary intent of this task is to find the factor as ...
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### Hackerrank challenge - Dictionaries and Maps

This is a solution for the Day 8 hackerrank.com challenge. The basic idea of the challenge is to create a mapping of names to phone numbers based on the the given input, and later look up the phone ...
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### The Genetic Code

This question is part of a series solving the Rosalind challenges. For the previous question in this series, see Wascally wabbits. The repository with all my up-to-date solutions so far can be found ...
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### BFS shortest path for Google Foobar “Prepare the Bunnies' Escape”

This is the Google Foobar puzzle "Prepare the Bunnies' Escape": You have maps of parts of the space station, each starting at a prison exit and ending at the door to an escape pod. The map is ...
351 views

### Project Euler #54 solution - follow-up

This is my second solution to Project Euler #54. You can find the original post here. Brief problem summary: The file, poker.txt, contains one-thousand random hands dealt to two players. Each line ...
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### Determine whether any permutation of a string is a palindrome

The task: Given a string, determine whether any permutation of it is a palindrome. For example, "carrace" should return true, since it can be rearranged ...
106 views

### Find the elements that appear only once

The task: Given an array of integers in which two elements appear exactly once and all other elements appear exactly twice, find the two elements that appear only once. For example, given ...
527 views

### Printing all the prime numbers between two bounds

I keep getting a time limit exceeded for this solution to SPOJ Prime1. I need to print all primes within a given interval (with intervals as large as 105, and numbers as large as 109). I've tried ...
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### Finding Pythagorean Triple that sums to 1000

I am doing this Project Euler Question #9: A Pythagorean triplet is a set of three natural numbers, $a < b < c$, for which, $$a^2 + b^2 = c^2$$ For example, \\$3^2 + 4^2 = 9 + 16 = ...
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### BFS shortest path for Google Foobar challenge “Prepare the Bunnies' Escape”

This is the Google Foobar challenge "Prepare the Bunnies' Escape": You have maps of parts of the space station, each starting at a prison exit and ending at the door to an escape pod. The map is ...
634 views

### Project Euler #3 solution

I'm trying to solve Project Euler problem #3, which asks: The prime factors of 13195 are 5, 7, 13 and 29. What is the largest prime factor of the number 600851475143 ? Can you please review the ...
589 views

### Finding a word within a pre-defined set using a search string with wildcards

The other day I was intrigued by this question (originally from here): Write a program that answers YES/NO search queries containing * placeholders. Example: if the data you have is (hazem, ahmed,...
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### Finding the sum of all the multiples of 3 or 5 below 1000

As a Lisp (and functional programming) newbie, I wrote the following code that finds the sum of all the multiples of 3 or 5 below 1000, and I suspect that it is lousy: ...
457 views

### Add Two Numbers given in Reverse Order from a Linked List

Updated Question Problem Description You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order and each of their nodes contain a ...