leetcode-771-easy

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.

思路一：存 map, 最后遍历字符串即可

public int numJewelsInStones(String jewels, String stones) {

    Set<Character> set = new HashSet<>();
    for (int i = 0; i < jewels.length(); i++) {
        set.add(jewels.charAt(i));
    }

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

    return count;
}