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771. 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.

Solution:

class Solution {
    public int numJewelsInStones(String jewels, String stones) {
        Set<Character> set = new HashSet<Character>();

        for (int i = 0; i < jewels.length(); i++){
            set.add(jewels.charAt(i));
        }

        int result = 0;

        for (int i = 0; i < stones.length(); i++){
            char cur = stones.charAt(i);
            if (set.contains(cur)){
                result++;
            }
        }

        return result;
    }
}

// TC: O(n)
// SC: O(1)