LeetCode 771. Jewels and Stones-优快云博客

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博客围绕LeetCode上一道宝石计数算法题展开。题目给出代表宝石类型的字符串J和拥有的石头字符串S，需计算S中宝石数量。给出了示例及注意事项，还提及题目为简单题，并给出了两种AC代码。

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 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.

这道题属于简单题

AC代码1

public int numJewelsInStones_2(String J, String S) {

        int count=0 ;

        for(int i=0; i<S.length() ; i++){
            char cur = S.charAt(i);
            if(J.indexOf(cur) != -1){
                count++;
            }
        }

        return count;

    }

AC代码2

//replaceAll，利用正则表达式进行替换，[^J]表示遍历S的每个字符，当字符不属于J的字符时替换为"".
 public int numJewelsInStones_1(String J, String S) {
        return S.replaceAll("[^" + J + "]", "").length();
    }