Python
hard
Algorithms
Triple sorting: frequency, length, lexicographically
Given a list of strings. Sort the strings according to three criteria: first by decreasing frequency of occurrence of th…
✅ 0 solved
📅 2026-05-11
Kotlin
medium
Math
Sum of prime numbers in a range
Write a program that finds the sum of all prime numbers in a given range [a, b] inclusive. A prime number is a natural n…
✅ 0 solved
📅 2026-05-11
Java
hard
Collections
Maximum frequency with substrings
Given a string S consisting of lowercase Latin letters. It is necessary to find the maximum length of a substring in whi…
✅ 0 solved
📅 2026-05-11
PHP
easy
Date
Determining the day of the week by date
Write a program that takes a date in the format 'YYYY-MM-DD' and determines the day of the week for that date. Output th…
✅ 0 solved
📅 2026-05-11
C#
medium
Algorithms
Sorting a matrix in descending order of column sums
Given a rectangular matrix of integers. It is necessary to sort the columns of the matrix in descending order of the sum…
✅ 0 solved
📅 2026-05-11
JavaScript
hard
Algorithms
Sorting by a hybrid algorithm of merge sort and quick sort
Implement a hybrid sorting algorithm that uses quicksort to partition the array, and if the size of a subarray is less t…
✅ 0 solved
📅 2026-05-11
C++
medium
Algorithms
Sorting by weights
Given an array of integers. Sort it in ascending order by the sum of the digits of each number (the weight of the number…
✅ 0 solved
📅 2026-05-11
TypeScript
easy
Generics
Generalized array merging with duplicate removal
Write a generic function `mergeUnique` that takes two arrays of the same type and returns a new array containing all uni…
✅ 0 solved
📅 2026-05-11
Swift
medium
Math
Sum of squares of prime numbers in a range
Two natural numbers A and B are given (1 …
✅ 0 solved
📅 2026-05-11
Kotlin
easy
Data classes
Class for storing point coordinates
Create a data class Point with fields x and y of type Int. Write a function that takes two strings: the first contains t…
✅ 0 solved
📅 2026-05-11
PHP
hard
Regex
Decoding a regular expression with nested repetitions
Given a string containing an encoded regular expression in a special format: letters of the Latin alphabet (a-z) and dig…
✅ 0 solved
📅 2026-05-11
Go
medium
Math
Calculating the area of a triangle using vertex coordinates
Write a Go program that calculates the area of a triangle given the coordinates of its three vertices on a plane. The in…
✅ 0 solved
📅 2026-05-11
Rust
easy
Enums
Order status
Determine the order status by its code. The order code is an integer from 0 to 4. 0 — 'New', 1 — 'Processing', 2 — 'Ship…
✅ 0 solved
📅 2026-05-11
Java
medium
Algorithms
Sorting by parity and value
Given an array of integers. It is necessary to sort it so that all even numbers come first in ascending order, followed …
✅ 0 solved
📅 2026-05-11
C#
easy
Math
Sum of digits of a three-digit number
Write a program that takes a three-digit integer and calculates the sum of its digits. The number can be positive or neg…
✅ 0 solved
📅 2026-05-11
Python
medium
Math
Sum of divisors of a number
Given a natural number n. Find the sum of all its divisors (including 1 and the number itself). If the number is prime, …
✅ 0 solved
📅 2026-05-11
C++
easy
Math
Sum of even numbers from A to B
The input consists of two integers A and B. It is necessary to find the sum of all even numbers in the range from A to B…
✅ 0 solved
📅 2026-05-11
JavaScript
medium
Math
Sum of squares of prime numbers in the interval
Write a function that takes two integers a and b (a ≤ b). It is necessary to find all prime numbers in the interval [a, …
✅ 0 solved
📅 2026-05-11
TypeScript
hard
Classes
Implementation of the Observer pattern with priority and filtering support
Create a class `EventBus` that implements the Observer pattern. It should allow subscribing to events with a specified p…
✅ 0 solved
📅 2026-05-11
Kotlin
hard
Classes
Class for managing a complex hierarchy of geometric shapes with intersection checking
Create classes to represent geometric shapes: Point, Circle, Rectangle. The Point class contains x and y coordinates (Do…
✅ 0 solved
📅 2026-05-11
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