## 题目描述：

You are playing the following Bulls and Cows game with your friend: You write a 4-digit secret number and ask your friend to guess it, each time your friend guesses a number, you give a hint, the hint tells your friend how many digits are in the correct positions (called "bulls") and how many digits are in the wrong positions (called "cows"), your friend will use those hints to find out the secret number.

For example:

```Secret number:  1807
Friend's guess: 7810```

Hint: `1` bull and `3` cows. (The bull is `8`, the cows are `0`, `1` and `7`.)

According to Wikipedia: "Bulls and Cows (also known as Cows and Bulls or Pigs and Bulls or Bulls and Cleots) is an old code-breaking mind or paper and pencil game for two or more players, predating the similar commercially marketed board game Mastermind. The numerical version of the game is usually played with 4 digits, but can also be played with 3 or any other number of digits."

Write a function to return a hint according to the secret number and friend's guess, use `A` to indicate the bulls and `B` to indicate the cows, in the above example, your function should return `1A3B`.

You may assume that the secret number and your friend's guess only contain digits, and their lengths are always equal.

## 题目大意：

```神秘数字：  1807

## 解题思路：

bull = secret与guess下标与数值均相同的数字个数

cow = secret与guess中出现数字的公共部分 - bull

## Python代码（使用Counter）：

``````class Solution(object):
def getHint(self, secret, guess):
"""
:type secret: str
:type guess: str
:rtype: str
"""
bull = sum(map(operator.eq, secret, guess))
sa = collections.Counter(secret)
sb = collections.Counter(guess)
cow = sum((sa & sb).values()) - bull
return str(bull) + 'A' + str(cow) + 'B'
``````

## Python代码：

``````def getHint(self, secret, guess):
bulls = sum(map(operator.eq, secret, guess))
both = sum(min(secret.count(x), guess.count(x)) for x in '0123456789')
return '%dA%dB' % (bulls, both - bulls)
``````

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