Smallest Multiple of N with Zeros and Ones, Java

Smallest Multiple of N with Zeros and Ones

//'main' method must be in a class 'Rextester'.
//Compiler version 1.8.0_111

import java.util.*;
import java.lang.*;

class Rextester
{  
    public static void main(String args[])
    {
        Solution sol = new Solution();
        System.out.println(Arrays.toString(sol.minMultiple(7)));
        System.out.println(Arrays.toString(sol.fastMinMultiple(7)));
        System.out.println(Arrays.toString(sol.minMultiple(27)));
        System.out.println(Arrays.toString(sol.fastMinMultiple(27)));
        //System.out.println(Arrays.toString(sol.minMultiple(1)));
        //System.out.println(Arrays.toString(sol.fastMinMultiple(1)));
        for (int i = 1; i < 30; i++) {
            long[] gold = sol.minMultiple(i);
            String[] test = sol.fastMinMultiple(i);
            if (gold[1] != Long.valueOf(test[1])) {
                System.out.println(Arrays.toString(gold));
                System.out.println(Arrays.toString(test));    
            }
        }
        System.out.println("All good!");
    }
}

class Solution {
    public String[] fastMinMultiple(int n) {
        Deque<Object[]> que = new ArrayDeque<>();
        // [0] partial product (String)
        // [1] multiplier (String)
        // [2] carry (Integer)
        String[] res = null;
        que.offer(new Object[] {"", "", 0});
        while (!que.isEmpty() && res == null) {
            for (int j = que.size(); j > 0; j--) {
                Object[] objs = que.poll();
                String result = (String) objs[0];
                String multiplier = (String) objs[1];
                Integer carry = (Integer) objs[2];
                //System.out.println(Arrays.toString(new String[] {result, multiplier, String.valueOf(carry)}));
                for (int i = 0; i <= 9; i++) {
                    if (carry == 0 && i == 0) continue;
                    int num = n*i + carry;
                    if (isZeroOne(num)) {
                        String[] potential = new String[] {String.valueOf(num) + result, String.valueOf(i) + multiplier};
                        if (res == null || res[1].compareTo(String.valueOf(i) + multiplier) > 0) {
                            res = potential;
                        }
                        //System.out.println(Arrays.toString(potential));
                    } else if ((num % 10) <= 1) {
                        que.offer(new Object[] {
                            String.valueOf(num % 10) + result,
                            String.valueOf(i) + multiplier,
                            num / 10});
                    }
                }
            }
        }
        return res;
    }

public long[] minMultiple(int n) {
        assert n > 0;
        long res = n, i = 1;
        while (res > 0) {
            if (isZeroOne(res)) return new long[] {res, i};
            res += n;
            i++;
        } 
        return null;
    }

public boolean isZeroOne(long n) {
        while (n != 0) {
            long d = n % 10;
            if (d != 0 && d != 1) return false;
            n /= 10;
        }
        return true;
    }
}


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