Jewels and Stones

就是字符找匹配

class Solution {
    public int numJewelsInStones(String J, String S) {
        int res = 0;
        int[] count = new int[255];
        for(int i = 0 ; i < S.length(); i++) {
            count[S.charAt(i)]++;
        }
        
        for(int i = 0 ; i < J.length(); i++) {
            res += count[J.charAt(i)];
        }
        
        return res;
    }
}