LeetCode 0771 Jewels and Stones【宝石与石头，哈希】

LeetCode 771：宝石与石头的哈希解决方案

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该博客介绍了LeetCode第771题——宝石与石头的问题，通过使用哈希表来解决。文章提供了题意解析、思路讲解以及对应的代码实现。

题目链接 771. Jewels and Stones |

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.

题意

字符串 J 中每个字符为宝石，字符串 S 中的每个字符为自己拥有的石头，想知道自己拥有多少宝石。

区分大小写

思路1

使用一个哈希表记录所有的宝石
遍历 S 中的所有石头，使用 ans 记录宝石的数量

代码1

class Solution {
public:
    int numJewelsInStones(string J, string S) {
        bool ch[256] = {true};
        for(const auto &it : J)
            ch[it] = true;
        int ans = 0;
        for(const auto &it : S)
            if(ch[it])
                ans++;
        return ans;
    }
};