# leetcode\_771

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.

## Solutions

1. **straight forward**

```cpp
class Solution {
public:
    int numJewelsInStones(string J, string S) {
        vector<bool> isjewel(128);
        for (auto c : J) isjewel[c] = true;

        return count_if(S.begin(), S.end(), [&](int c){ return isjewel[c]; });
    }
};
```