Jewels and Stones

You're given strings J representing the types of stones that are jewels, and S representing the stones you have. Each character in S is a type of stone you have. You want to know how many of the stones you have are also jewels.

The letters in J are guaranteed distinct, and all characters in J and S are letters. Letters are case sensitive, so "a" is considered a different type of stone from "A".

Example 1:

Input: J = "aA", S = "aAAbbbb" Output: 3 Example 2:

Input: J = "z", S = "ZZ" Output: 0 Note:

S and J will consist of letters and have length at most 50. The characters in J are distinct.

Solution: Using hash table or array

    int numJewelsInStones(string J, string S) {
        int m[256] = {false};
        for (auto c: J) m[c] = true;

        int count = 0;
        for (auto c: S) {
            if (m[c]) count++;
        }
        return count;
    }

Solution: Using unordered_set

    int numJewelsInStones(string J, string S) {
        unordered_set<char> s(J.begin(), J.end());
        int count = 0;
        for (auto c: S) {
            if (s.count(c)) count++;
        }
        return count;
    }