771. Jewels and Stones

题目

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 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.

题目大意

给定字符串 J 代表石头中宝石的类型，和字符串 S 代表你拥有的石头。S 中每个字符代表了一种你拥有的石头的类型，你想知道你拥有的石头中有多少是宝石。

J 中的字母不重复，J 和 S 中的所有字符都是字母。字母区分大小写，因此 "a" 和 "A" 是不同类型的石头。

解题思路

• 给出 2 个字符串，要求在 S 字符串中找出在 J 字符串里面出现的字符个数。这是一道简单题。