383_赎金信

类型：字符串

• 383. 赎金信 💚

  https://leetcode-cn.com/problems/ransom-note/

  ❓ 判断杂志 magazine 中的字符能否构成赎金信 ransom。

  💡 哈希

  遍历 magazine，构建哈希表，字符为键，出现次数为值。

  遍历 ransom，检验各个字符的出现次数，

  class Solution:
      def canConstruct(self, ransomNote: str, magazine: str) -> bool:
          hashMap = {}
          for c in magazine:
              if c in hashMap:
                  hashMap[c] += 1
              else:
                  hashMap[c] = 1
          for c in ransomNote:
              if not c in hashMap:
                  return False
              elif hashMap[c] == 1:
                  del hashMap[c]
              else:
                  hashMap[c] -= 1
          return True

  时间复杂度：O(m + n)，空间复杂度：O(m)