10.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.

Example 1:
Input: J = "aA", S = "aAAbbbb"
Output: 3

Example 2:
Input: J = "z", S = "ZZ"
Output: 0

Solution : (Using Hashset)

class Solution
{
public:
    int numJewelsInStones(string J, string S)
    {

        unordered_set<char> s;
        int c = 0;
        for (int i = 0; i < J.length(); i++)
        {
            if (s.find(J[i]) == s.end())
            {
                s.insert(J[i]);
            }
        }

        for (int i = 0; i < S.length(); i++)
        {
            if (s.find(S[i]) != s.end())
            {
                c++;
            }
        }

        return c;
    }
};

Time Complexity: O(n), Space Complexity: O(n)