题目
难度：easy
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:
+ S and J will consist of letters and have length at most 50.
+ The characters in J are distinct.
第一次解法
/**
* @param {string} J
* @param {string} S
* @return {number}
*/
var numJewelsInStones = function(J, S) {
var num = 0;
var l = S.length;
while(l>0){
if(J.indexOf(S.charAt(l-1))>-1){
num++
}
l--
}
return num
};
# runtime : 75ms
