2. Jewels and Stones.cpp

/*

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.

*/

class Solution {
public:
    int numJewelsInStones(string J, string S) 
    {
        int i=0,j,ctr=0;
        set<char>myset;
        
        for(auto x:J)
            myset.insert(x);
        
        for(j=0;j<S.size();j++)
            if(myset.count(S[j]))
                ctr++;
        
    return ctr;
    }
};


// Algorithm/Data Structure: HashSet 
// TC: O(n)
// SC: O(1)