Lanqiao Cup official website fill-in-the-blank question (square ten digits)

Question description

This question is a fill-in-the-blank question. You only need to calculate the result and use the output statement in the code to output the filled-in result.

Many 10-digit numbers can be formed from the 10 numbers from 0 to 9 without repetition or omission. There are also many of them that happen to be square numbers (the square of a number).

For example: 1026753849 is the smallest square number among them.

Please find out what is the largest square number among them?

operating restrictions

• Maximum running time: 1s
• Maximum running memory: 128M

import java.util.*;

public class Main {
    public static void main(String[] args) {
        for(long i=100000;i>6666;i--){
            if(check(i*i)==1){
                System.out.println(i*i);
                break;
            }
        }
    }
    public static int check(long n){
        int flag=1;
        int k=0;
        int[] f=new int[10];
        while(n>0){
            k=(int)(n%10);
            f[k]++;
            n=n/10;
            if (f[k] > 1) {
                flag = 0;
                break;
            }
        }
        return flag;
    }
}