Jewels and Stones

题目描述：

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.

解题思路：

此题难度为easy，遍历S中每个letter s并判断s是否在J中存在，若存在个数加一。

代码：

class Solution {
public:
    int numJewelsInStones(string J, string S) {
        int num = 0;
        for (auto s : S) {
            if (J.find(s) != string::npos)
                num++;
        }
        return num;
    }
};