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.
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: …
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