2 Lines, LINQ, fast solution
Approach\nSomeone had to post it anyway.\n\n# Complexity\n- Time complexity:\nO(n)\n\n- Space complexity:\nO(1)\n\n# Code\n\nusing System.Collections.Immutable;
# Approach\nSomeone had to post it anyway.\n\n# Complexity\n- Time complexity:\n$$O(n)$$\n\n- Space complexity:\n$$O(1)$$\n\n# Code\n```\nusing System.Collections.Immutable;\n\npublic class Solution\n{\n    public int CountConsistentStrings(string allowed, string[] words)\n    {\n        var allowedSet = allowed.ToImmutableHashSet();\n\n        return words.Count(w => w.All(allowedSet.Contains));\n    }\n}\n```
['C#']