Jewels and Stones
You're given strings jewels representing the types of stones that are jewels, and stones representing the stones you have. Each character in stones is a type of stone you have. You want to know how many of the stones you have are also jewels.
Letters are case sensitive, so "a" is considered a different type of stone from "A".
Example 1:
Input: jewels = "aA", stones = "aAAbbbb"
Output: 3
Example 2:
Input: jewels = "z", stones = "ZZ"
Output: 0
Constraints:
1 <= jewels.length, stones.length <= 50
jewels and stones consist of only English letters.
All the characters of jewels are unique.
思路一：存 map, 最后遍历字符串即可
public int numJewelsInStones(String jewels, String stones) {
Set<Character> set = new HashSet<>();
for (int i = 0; i < jewels.length(); i++) {
set.add(jewels.charAt(i));
}
int count = 0;
for (int i = 0; i < stones.length(); i++) {
if (set.contains(stones.charAt(i))) count++;
}
return count;
}