LeetCode #771 - Jewels and Stones

最新推荐文章于 2019-06-08 15:01:59 发布

原创最新推荐文章于 2019-06-08 15:01:59 发布 · 117 阅读

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本文解析了一种算法，用于计算给定字符串中特定字符（宝石）的数量。通过使用哈希映射，算法能高效地从一堆石头（字符串）中找出宝石（目标字符）。文章详细介绍了算法的实现过程及示例。

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.

class Solution {
public:
    int numJewelsInStones(string J, string S) {
        unordered_map<char,bool> hash;
        for(char c:J) hash[c]=true;
        int result=0;
        for(char c:S) if(hash.count(c)) result++;
        return result;
    }
};