题解 | #字符个数统计#

还是利用HashSet的特性，和HJ9差不多的思路

import java.util.*;
public class Main{
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while(sc.hasNext()){
            HashSet<Character> hs = new HashSet<>();
            StringBuffer bf = new StringBuffer(sc.nextLine());
            int sum = 0;
            for(int i = 0 ; i < bf.length(); i++){
                if(hs.add(bf.charAt(i)))
                    sum++;
            }
            System.out.println(sum);
        }
    }
}