leetcode Bulls and Cows

leetcode Bulls and Cows

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.)

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"

In this case, the 1st 1 in friend's guess is a bull, the 2nd or 3rd 1 is a cow, and your function should return "1A1B".

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

题目地址：leetcode Bulls and Cows

题意

写几个数字(secret)，让你猜（guess），如果guess中数字的位置和secret的位置一样，那么就是bull，如果guess中数字为secret中一样，但是有出现，则为cows。

现在给你secret和guess串，让你返回bull和cows的个数。

思路

相同位置数字相同的个数就是bull，这个不用解释~

那么cows怎么算呢? 统计下同一位置下但是数字不同种secret数字出现的个数，然后就可以用guess中同一位置数字不同，看在secret中是否出现~

class Solution(object):
    def getHint(self, secret, guess):
        """
        :type secret: str
        :type guess: str
        :rtype: str
        """
        if not secret or not guess: return '0A0B'
        bulls, cows, digits = 0, 0, [0 ] * 10
        for i in xrange(len(secret)):
            if secret[i] == guess[i]:
                bulls += 1
            else:
                digits[int(secret[i])] += 1

        for i in xrange(len(secret)):
            if secret[i] != guess[i] and digits[int(guess[i])] != 0:
                cows += 1
                digits[int(guess[i])] -= 1
        return str(bulls) + 'A' + str(cows) + 'B'