Guess The Number/Bulls & cows

Bulls and cows is also known as Mastermind, 4digits, guess the number ... The goal of the game is to guess the number with a minimum of attempts. In the beginning your phone generates a random number, and you try to guess this number. The opponent responds by announcing the number of matches: If the matching digits are on their right positions, they are "bulls", if they are on different positions, they are "cows".