题解 | 字符个数统计

import java.util.Scanner;
import java.util.HashSet;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        String str = in.next();
        HashSet<Character> hs = new HashSet<Character>();
        for (int i = 0; i < str.length(); i++)
            hs.add(str.charAt(i));
        System.out.println(hs.size());
    }
}