手写几个测试用例就知道了规律
0123456789 ==11
01123456789==22
0112233445566789=77
00112233445566778899=100
00112233445566778899==111

import java.util.Scanner;
public class Main {
    public static void main(String[] args){
        Scanner scanner = new Scanner(System.in);
        String s = scanner.nextLine();
        int[] ints = new int[10];
        for(int i = 0; i < s.length(); i++){
            ints[Integer.parseInt(String.valueOf(s.charAt(i)))] += 1;
        }
        //输出结果
        ints[0]++;//0加一位
        int min = Integer.MAX_VALUE, index = -1;
        for(int i = ints.length - 1; i >= 0; i--){
            if(ints[i] < min){
                min = ints[i];
                index = min;
            }
        }
        String res = "";
        for(int i = 0; i < min; i++){
            res += index;
        }
        if(index == 0){
            res = 1 + res;
        }else{
            res = index + res;
        }
        System.out.println(res);    
    }
}