383. Ransom Note

class Solution {
public:
    bool canConstruct(string ransomNote, string magazine)
    {
        vector<int> freq(26);

        for(auto& c : magazine) ++freq[ c - 'a'];

        for(int i = 0; i < ransomNote.size(); i++)
        {
            int c = ransomNote[i] - 'a';
            if (--freq[c] < 0) return false;
        }
        return true;
    }
};

• T: $O(N)$
• S: $O(1)$