Given a pattern and a string str, find if str follows the same pattern.

Given a string that contains only digits 0-9 and a target value, return all possibilities to add binary operators (not unary) +, -, or * between the digits so t...

You task is to find minimal natural number N, so that N! contains exactly Q zeroes on the trail in decimal notation. As you know N! = 12…*N. For example, 5! = 1...

Read integers A and B from input file and write their sum in output file.

There is sequence 1, 12, 123, 1234, …, 12345678910, … . Given first N elements of that sequence. You must determine amount of numbers in it that are divisible b...

You are given natural numbers a and b. Find a^b-b^a.

The sequence of non-negative integers A1, A2, …, AN is given. You are to find some subsequence Ai1, Ai2, …, Aik (1 <= i1 < i2 < … < ik <= N) such, that Ai1 XOR ...

Inspired by a “Little Bishops” problem, Petya now wants to solve problem for rooks.

The set [1,2,3,…,n] contains a total of n! unique permutations.

The n-queens puzzle is the problem of placing n queens on an n×n chessboard such that no two queens attack each other.