You are playing the following Bulls and Cows game with your friend: You write down a number and ask your friend to guess what the number is. Each time your friend makes a guess, you provide a hint that indicates how many digits in said guess match your secret number exactly in both digit and position (called "bulls") and how many digits match the secret number but locate in the wrong position (called "cows"). Your friend will use successive guesses and hints to eventually derive the secret number.

For example:

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

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"

Please note that both secret number and friend's guess may contain duplicate digits, for example:

Secret number:  "1123"
Friend's guess: "0111"

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

Credits:
Special thanks to @jeantimex for adding this problem and creating all test cases.

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解題分析：

     對於此題的理解是這樣的，首選給出兩個字串，一個是secret   一個是guess，

然後分別按著 secert 的每一位去對比guess對應位置，若對應位置的元素值相同，則我們在bull上加一，如果沒有的話我們在cow上加一（注：此處需要將重複的數字去重，多個重複的我們只算一次）。

   方法，首先選出對應位置的加在bull，然後在剩餘的數字中去重，最後加到cow中。

# -*- coding:utf-8 -*-
__author__ = 'jiuzhang'
class Solution(object):
    def getHint(self, secret, guess):
        digit = {}
        bull = 0
        for i in xrange(len(secret)):
            if guess[i] == secret[i]:
                bull += 1
            else:
                if guess[i] not in digit:
                    digit[guess[i]] = 1
                else:
                    digit[guess[i]] += 1
        cow = 0
        for i in xrange(len(secret)):
            if guess[i] != secret[i] and secret[i] in digit and digit[secret[i]]>0:
               digit[secret[i]] -= 1
               cow += 1
        return str(bull) + 'A' + str(cow) + 'B'