GuilinDev

Lc0771

05 August 2008

771 Jewels and Stones

原题概述

You’re given strings 

1

J
representing the types of stones that are jewels, and 
1

S
representing the stones you have. Each character in 
1

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 

1

J
are guaranteed distinct, and all characters in 
1

J
and 
1

S
are letters. Letters are case sensitive, so 
1

"a"
is considered a different type of stone from 
1

"A"
.

Example 1:

1
2

Input: J = "aA", S = "aAAbbbb"
Output: 3

Example 2:

1
2

Input: J = "z", S = "ZZ"
Output: 0

Note:

  • 1

    S
    and 
    1

    J
    will consist of letters and have length at most 50.
  • The characters in 
    1

    J
    are distinct.

题意和分析

这道题J中的字符全是珠宝分类，没有重复，S中的字符是石头或者珠宝，找出S中所有是珠宝的字符。暴力搜索就是把J中字符分别拿到S中去对比下，match一次就+1；decent一点的做法则是用hashset把J中的字符装入（因为没重复），然后把S中的字符分别来看是否存在。

代码

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class Solution {
    public int numJewelsInStones(String J, String S) {
        int result = 0;
        Set<Character> jset = new HashSet<>();
        for (char j : J.toCharArray()) {
            jset.add(j);
        }
        for (char s : S.toCharArray()) {
            if (jset.contains(s)) {
                result++;
            }
        }
        return result;
    }
}
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