题解 | #字符个数统计#

import java.util.BitSet;
import java.util.Map;
import java.util.Scanner;
import java.util.TreeMap;

/**
 * @ProjectName: leetcode
 * @Package: com.company.niuke
 * @ClassName: MergeMap
 * @Author: Administrator
 * @Description: 合并
 * @Date: 2022/2/16 21:58
 * @Version: 1.0
 */

public class Main {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String line = scanner.next();
        //总共有128个字符。字需要用128位
        BitSet bitSet = new BitSet(128);
        for (char c : line.toCharArray()) {
            //判断字符c是否已出现
            if (!bitSet.get(c)) {
                //未出现就设置为已出现
                bitSet.set(c);
            }
        }
        //统计有多少字符已出现过
        System.out.println(bitSet.cardinality());
    }
}