771. Jewels and Stones

package LeetCode_771

/**
 * 771. Jewels and Stones
 * https://leetcode.com/problems/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 S is 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:
1. S and J will consist of letters and have length at most 50.
2. The characters in J are distinct.
 * */

class Solution {
    /*
    * solution: array, calculate how many character of J in S, Time:O(j+s), Space:O(1)
    * */
    fun numJewelsInStones(J: String, S: String): Int {
        var count = 0
        //because case sensitive
        val mapOfS = IntArray(128)
        for (c in S.toCharArray()) {
            //calculate count of char in S
            mapOfS[c.toInt()]++
        }
        for (c in J) {
            //get the count from S
            count += mapOfS[c.toInt()]
        }
        return count
    }
}