边工作边刷题：70天一遍leetcode: day 53

Bulls and Cows

要点：类似于Word Pattern，guess和secret要存成两个counts<int, int>，因为guess中了的可能在secret之前出现，vice versa。另一种方法是可以多遍统计：先过一遍secret，然后过一遍guess统计cows，最后统计bulls调整cows

class Solution(object):
    def getHint(self, secret, guess):
        """
        :type secret: str
        :type guess: str
        :rtype: str
        """
        from collections import defaultdict
        bulls,cows = 0,0
        cowskey = defaultdict(int)
        cowsval = defaultdict(int)
        for i in xrange(len(secret)):
            if secret[i]==guess[i]:
                bulls+=1
                continue
            
            if guess[i] in cowskey and cowskey[guess[i]]>0:
                cows+=1
                cowskey[guess[i]]-=1
            else:
                cowsval[guess[i]]+=1

            if secret[i] in cowsval and cowsval[secret[i]]>0:
                cows+=1
                cowsval[secret[i]]-=1
            else:
                cowskey[secret[i]]+=1
        
        return str(bulls)+'A'+str(cows)+'B'