383. Ransom Note

• Time: $O(|\texttt{ransomNote}| + |\texttt{magazine}|)$
• Space: $O(26) = O(1)$

C++JavaPython

class Solution {
 public:
  // Similar to 0242. Valid Anagram
  bool canConstruct(string ransomNote, string magazine) {
    vector<int> count(26);

    for (const char c : magazine)
      ++count[c - 'a'];

    for (const char c : ransomNote) {
      if (count[c - 'a'] == 0)
        return false;
      --count[c - 'a'];
    }

    return true;
  }
};

class Solution {
  public boolean canConstruct(String ransomNote, String magazine) {
    int[] count = new int[26];

    for (final char c : magazine.toCharArray())
      ++count[c - 'a'];

    for (final char c : ransomNote.toCharArray()) {
      if (count[c - 'a'] == 0)
        return false;
      --count[c - 'a'];
    }

    return true;
  }
}

class Solution:
  def canConstruct(self, ransomNote: str, magazine: str) -> bool:
    count1 = collections.Counter(ransomNote)
    count2 = collections.Counter(magazine)
    return all(count1[c] <= count2[c] for c in string.ascii_lowercase)