Simple string expansion in Java
The challenge
Consider the following expansion:
// because "ab" repeats 3 times
solve("3(ab)") == "ababab"
// because …Technical Articles
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Hamming Numbers in Java
The challenge
A Hamming number is a positive integer of the form 2i3j5k, for some non-negative integers i, j, and k.
Write a function that computes …
Read Article →Block sequence in Java
The challenge
Consider the following array:
[1, 12, 123, 1234, 12345, 123456, 1234567, 12345678, 123456789, 12345678910, 1234567891011...]
If we join …
Read Article →Roman Numerals Helper in Java
The challenge
Create a RomanNumerals class that can convert a roman numeral to and from an integer value. It should follow the API demonstrated in the …
Read Article →Closest pair of points in linearithmic time in Java
The challenge
Given a number of points on a plane, your task is to find two points with the smallest distance between them in linearithmic O(n log n) …
Read Article →Find sum of top-left to bottom-right diagonals in Java
The challenge
Given a square matrix (i.e. an array of subarrays), find the sum of values from the first value of the first array, the second value of …
Read Article →Sweeping trees in Java
The challenge
You will be given a list of strings representing nodes in a rooted tree. A visual representation of a very simple rooted tree could be: …
Read Article →Detect Pangram in Java
The challenge
A pangram is a sentence that contains every single letter of the alphabet at least once. For example, the sentence “The quick …
Read Article →Remove the parentheses in Java
The challenge
In this challenge you are given a string for example:
"example(unwanted thing)example"
Your task is to remove everything inside …
Read Article →What century is it in Java
The challenge
Return the century of the input year. The input will always be a 4 digit string, so there is no need for validation.
Examples …
Read Article →Lost number in number sequence in Java
The challenge
An ordered sequence of numbers from 1 to N is given. One number might have deleted from it, then the remaining numbers were mixed. Find …
Read Article →Simple string reversal in Java
The challenge
In this challenge, we are going to reverse a string while maintaining the spaces (if any) in their original place.
For example: …
Read Article →int32 to IPv4 in Java
The challenge
Take the following IPv4 address: 128.32.10.1
This address has 4 octets where each octet is a single byte (or 8 bits).
- 1st octet
128has …
Perimeter of squares in a rectangle in Java
The challenge
The drawing shows 6 squares the sides of which have a length of 1, 1, 2, 3, 5, 8. It’s easy to see that the sum of the perimeters …
Read Article →Palindrome chain length in Java
The challenge
Number is a palindrome if it is equal to the number with digits in reversed order. For example, 5, 44, 171, 4884 are palindromes, and 43 …
String array duplicates in Java
The challenge
You are given an array of strings and your task is to remove all consecutive duplicate letters from each string in the array.
For …
Read Article →Even or Odd Array Sum in Java
The challenge
Given a list of numbers, determine whether the sum of its elements is odd or even.
Give your answer as a string matching "odd" …
String Permutations in Java
The challenge
In this challenge, you have to create all permutations of an input string and remove duplicates if present. This means you have to …
Read Article →Remove a Specific Element of an Array in Java
The challenge
You will be given a certain array of length n, such that n > 4, having positive and negative integers but there will be no zeroes and …
Upside down numbers in Java
The challenge
Consider the numbers 6969 and 9116. When you rotate them 180 degrees (upside down), these numbers remain the same. To clarify, if we …
Rotate matrix counter-clockwise N times in Java
The challenge
In this challenge your mission is to rotate matrix counter-clockwise N times.
So, you will have 2 inputs:
1) matrix
2) a number, how …Unable to import module “lambda_function”: No module named “pymysql”
If you receive the following error message when trying to run pymysql on AWS Lambda:
Unable to import module "lambda_function": No module …
Square Matrix Multiplication in Java
The challenge
Write a function that accepts two square (NxN) matrices (two dimensional arrays), and returns the product of the two. Only square …
Count the divisible numbers in Java
The challenge
Complete the function that takes 3 numbers x, y and k (where x ≤ y), and returns the number of integers within the range [x..y] (both …