299. Bulls and Cows

problem

ou 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"
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.

猜数字游戏

solution

• 先判断元素相同，相同在两个列表内移除元素
• 后判断元素存在，存在在被判断列表内移除元素
• 缺陷在于删除list元素，时间复杂度

class Solution(object):
    def getHint(self, secret, guess):
        """
        :type secret: str
        :type guess: str
        :rtype: str
        """
        bulls = 0
        cows = 0
        secret, guess = list(secret), list(guess)
        for i in range(len(secret))[::-1]:
            if secret[i] == guess[i]:
                bulls += 1
                del secret[i]
                del guess[i]
        for element in guess:
            if element in secret:
                cows += 1
                secret.remove(element)
                
        return '{bulls}A{cows}B'.format(bulls=bulls,cows=cows)

discuss

增加了一个list，储存0-9，如果不等且secret中存在，对应数字+1；

class Solution(object):
    def getHint(self, secret, guess):
        """
        :type secret: str
        :type guess: str
        :rtype: str
        """
        repo=[0]*10
        A=0
        B=0
        for i in range(len(secret)):
            if secret[i]==guess[i]:
                A+=1
            else:
                repo[int(secret[i])]+=1
        for i in range(len(secret)):
            if secret[i]!=guess[i] and repo[int(guess[i])]>0:
                B+=1
                repo[int(guess[i])]-=1
        
        return '%dA%dB'%(A,B)