Leetcode 771. Jewels and Stones

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

The letters in J are guaranteed distinct, and all characters in J and S are letters. Letters are case sensitive, so "a" is considered a different type of stone from "A".

Example 1:

Input: J = "aA", S = "aAAbbbb"
Output: 3

Example 2:

Input: J = "z", S = "ZZ"
Output: 0

Note:

• S and J will consist of letters and have length at most 50.
• The characters in J are distinct.

Code (Java):

?

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class Solution {     public int numJewelsInStones(String J, String S) {         if (J == null || J.length() == 0 || S == null || S.length() == 0) {             return 0;         }                   int ans = 0;                   boolean[] dictS = new boolean[26];         boolean[] dictL = new boolean[26];                   // step 1: pre-process the string J and put chars into the dict         //         for (int i = 0; i < J.length(); i++) {             char c = J.charAt(i);             if (c >= 'a' && c <= 'z') {                 dictS[c - 'a'] = true;             } else {                 dictL[c - 'A'] = true;             }         }                   // step 2: check each char in S and see if it's in the dict         //         for (int i = 0; i < S.length(); i++) {             char c = S.charAt(i);             if (c >= 'a' && c <= 'z' && dictS[c - 'a']) {                 ans++;             } else if (c >= 'A' && c <= 'Z' && dictL[c - 'A']) {                 ans++;             }         }                   return ans;     } }