【leetcode】1189. Maximum Number of Balloons

题目如下：

Given a string text, you want to use the characters of text to form as many instances of the word "balloon" as possible.

You can use each character in text at most once. Return the maximum number of instances that can be formed.

Example 1:

Input: text = "nlaebolko"
Output: 1

Example 2:

Input: text = "loonbalxballpoon"
Output: 2

Example 3:

Input: text = "leetcode"
Output: 0

Constraints:

• 1 <= text.length <= 10^4
• text consists of lower case English letters only.

解题思路：题目很简单，求出text中b,a,l,o,n这五个字符的出现次数的最小值即可。但有两点需要注意，一是text必须同时包含这五个字符，而是l和o是要算双份。

代码如下：

class Solution(object):
    def maxNumberOfBalloons(self, text):
        """
        :type text: str
        :rtype: int
        """
        dic = {}
        char_list = ['b','a','l','o','n']
        res = float('inf')
        for i in text:
            if i not in char_list:
                continue
            dic[i] = dic.setdefault(i,0) + 1
        if len(char_list) != len(dic):
            return 0
        for k,v in dic.iteritems():
            if k in ('l','o'):
                res = min(res,v/2)
            else:
                res = min(res,v)
        return res