LeetCode - Jewels and Stones

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

Letters are case sensitive, so "a" is considered a different type of stone from "A".

 

Example 1:

Input: jewels = "aA", stones = "aAAbbbb"
Output: 3
Example 2:

Input: jewels = "z", stones = "ZZ"
Output: 0
 

Constraints:

1 <= jewels.length, stones.length <= 50
jewels and stones consist of only English letters.
All the characters of jewels are unique.

class Solution {
    public int numJewelsInStones(String jewels, String stones) {
        Map<Character, Integer> map = new HashMap<>();
        int count = 0;
        for (int i = 0; i < jewels.length(); i++) {
            map.put(jewels.charAt(i), 0);
        }
        for (int i = 0; i < stones.length(); i++) {
            if (map.containsKey(stones.charAt(i))) {
                count ++;
            }
        }
        return count;
    }
}