1.題目

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

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.

2.程式碼

class Solution {
public:
    int numJewelsInStones(string J, string S) {
        int num =0;
        set<char>set;
        for(int i = 0;i<J.length();i++)
            set.insert(J[i]);
        for(int i = 0;i<S.length();i++) {
            if(set.count(S[i])) { num++; }//如果S中的字元在J中則num++
        }
        return num;
    }
};