题解 | #字符集合#

import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static String func(String str) {
        boolean[] arr = new boolean[128];
        StringBuilder sb = new StringBuilder();

        for (int i = 0; i < str.length(); i++) {
            char ch = str.charAt(i);
            if (!arr[ch]) {
                sb.append(ch);
                arr[ch] = true;
            }
        }
        return sb.toString();
    }



    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while (sc.hasNextLine()) {
            String str = sc.nextLine();
            String ret = func(str);
            System.out.println(ret);
        }
    }
}