题解 | #华为no.10 字符个数统计#

利用hashset的add特性完成答题

public class Main {
    public static void main(String[] args) {
        //计算字符串中不重复的个数
        Scanner sc = new Scanner(System.in);
        String s = sc.next().toLowerCase();
        char[] c = s.toCharArray();
        HashSet<Character> set = new HashSet<>();
        int count = 0;
        for (int i=0;i<c.length;i++) {
            if (set.add(c[i])) {
                count++;
            }
        }
        System.out.println(count);
    }
}