GuessNumber (Bulls and Cows)

Numbers (Bulls and Cows) is a roughly in the middle of twentieth Century appeared in England puzzle game. Rules of the game is simple, but it tests rigorous and patience. At a game begins, the automatic generation of a four digit number will be generated, and the four digit number is not the same. When you guess a number, will get a (n)A(m)B, including A in front of the number indicates the number of the correct position number, and B before the number indicates the number of correct and incorrect number of locations and the number of. If the correct answer is 5234, and if your input is 5346, is 1A2B, the '5' position is correct, denoted as 1A, while '5234' contains '3' and '4', but the two number are not on the correct position, therefore, denoted as 2B, it's 1A2B. Then according to the records of several A B continue to guess, until the guess (4A0B).
Enjoy it!