```python from collections import defaultdict class Solution: # 给你两个字符串：ransomNote和magazine，判断ransomNote能不能由magazine里面的字符构成。 def canConstruct(self, ransomNote: str, magazine: str) -> bool: n = len( ransomNote ) m = len( magazine ) if n > m: return False magazine_map = defaultdict( int ) for v in magazine: magazine_map[ v ] += 1 for v in ransomNote: if v not in magazine_map: return False if magazine_map[ v ] <= 0: return False magazine_map[ v ] -= 1 return True ```