Ransom Note - 卖萌的弱渣

Given  an  arbitrary  ransom  note  string  and  another  string  containing  letters from  all  the  magazines,  write  a  function  that  will  return  true  if  the  ransom   note  can  be  constructed  from  the  magazines ;  otherwise,  it  will  return  false.   

Each  letter  in  the  magazine  string  can  only  be  used  once  in  your  ransom  note.

Each letter in the magazine string can only be used once in your ransom note.

Note:

You may assume that both strings contain only lowercase letters.

canConstruct("a", "b") -> false
canConstruct("aa", "ab") -> false
canConstruct("aa", "aab") -> true

Solution

hash_map: (character, 出现次数)

(Ransom-Note.py) download

class Solution(object):
    def canConstruct(self, ransomNote, magazine):
        """
        :type ransomNote: str
        :type magazine: str
        :rtype: bool
        """
        hash_map = dict()
        for i in magazine:
            if i not in hash_map:
                hash_map[i] = 1
            else:
                hash_map[i] += 1
        for i in ransomNote:
            if i not in hash_map:
                return False
            if hash_map[i] == 0:
                return False
            hash_map[i] -= 1
        return True