Leetcode #771 | #Easy | [[Хэш-таблицы]]
## Идея
Просто set
## [[Big-O]]
- Время ```O(N+M)```
- Память  ```O(N)```
## Код
```Java
class Solution {
    public int numJewelsInStones(String jewels, String stones) {
        Set<Character> set = new HashSet<>();
        for (char c : jewels.toCharArray()) set.add(c);
        int res = 0;
        for (char c : stones.toCharArray()) if (set.contains(c)) res++;
        return res;
    }
}
```