383.md

383 Ransom Note

Description

link

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Solution

collections.Counter minus:

>>> c = Counter(a=3, b=1)
>>> d = Counter(a=1, b=2)
>>> c + d                       # add two counters together:  c[x] + d[x]
Counter({'a': 4, 'b': 3})
>>> c - d                       # subtract (keeping only positive counts)
Counter({'a': 2})
>>> c & d                       # intersection:  min(c[x], d[x])
Counter({'a': 1, 'b': 1})
>>> c | d                       # union:  max(c[x], d[x])
Counter({'a': 3, 'b': 2})

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Code

O(n)

class Solution:
    def canConstruct(self, ransomNote: str, magazine: str) -> bool:
        return not collections.Counter(ransomNote) - collections.Counter(magazine)