LeetCode 771. Jewels and Stones

問題：判斷石頭內是否存在符合的珠寶

解法：先預設石頭內沒有任何珠寶，石頭以及珠寶轉成陣列

forEach走訪每顆珠寶將透過reduce取得石頭蘊含珠寶數量並將其加總，回傳即可 JavaScript

/**
 * @param {string} jewels
 * @param {string} stones
 * @return {number}
 */
var numJewelsInStones = function (jewels, stones) {
    let searchArray = jewels.split("");
    let count = 0;
    searchArray.forEach(s => {
        let sum = stones.split("").reduce((sum, n) => sum + (n === s ? 1 : 0), 0);
        count += sum;
    })

    return count;
};