【卡片】【Java】

import java.io.*;
import java.util.*;

public class Main{
	
	static boolean check(int[]a,int num) {
		String str=String.valueOf(num);
		char[] ch=str.toCharArray();
				
		for(char c:ch) {
			if(a[Character.getNumericValue(c)]==0) {
				return false;
			}
			a[Character.getNumericValue(c)]--;
		}
		return true;
	}
	
    public static void main(String[] args) throws IOException{
    	
    	PrintWriter out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(System.out)));
		
    	int[] arr=new int[10];
    	Arrays.fill(arr, 2021);
    	
    	int cnt=1;
    	
    	while(check(arr,cnt)) {
    		cnt++;
    	}
    		
    	out.print(cnt-1);
    	
    	out.flush();
		out.close();
    }
}

答案：3181