Ratsun reitit

import com.sun.tools.jconsole.JConsoleContext;

import java.io.*;
import java.util.HashMap;
import java.util.Map;

public class Main {

    private static int koko = 0;
    private static int i = 0;

    private static Map<Coords, Integer> lauta = new HashMap<>();

    private static Map<Coords, Integer> uudet;

    static class Coords {
        public int x;
        public int y;

        public Coords(int x, int y) {
            this.x = x;
            this.y = y;
        }

        public boolean equals(Object o) {
            Coords c = (Coords)o;
            return c.x==x && c.y==y;
        }

        public void move(int x, int y) {
            x += this.x;
            y += this.y;

            //varmistaa että siirto on mahdollinen
            if(x > -1 && x < koko && y > -1 && y < koko) {
                Coords siirto = new Coords(x, y);
                uudet.put(siirto, i+1);
            }
        }

        public int hashCode() {
            return Integer.parseInt(x + "0" + y);
        }
    }

    synchronized public static void main(String[] args) {

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

        try {
            koko = Integer.parseInt(br.readLine().trim());

        } catch (IOException ioe) {
            System.out.println(ioe);
        }

        lauta.put(new Coords(0, 0), 0);

        int kokoToiseen = koko * koko;
        while (lauta.size() < kokoToiseen) {
            //boolean loytyyko = false;

            uudet = new HashMap<>();

            for (Coords coord : lauta.keySet()) {

                if (lauta.get(coord) == i) {
                    //loytyyko = true;

                    coord.move(1, 2);
                    coord.move(-1, 2);
                    coord.move(1, -2);
                    coord.move(-1, -2);

                    coord.move(2, 1);
                    coord.move(-2, 1);
                    coord.move(2, -1);
                    coord.move(-2, -1);
                };

            }

            //if(!loytyyko) {
            //    break;
            //}

            for (Map.Entry<Coords, Integer>  entry : uudet.entrySet()) {
                lauta.putIfAbsent(entry.getKey(), entry.getValue());
            }

            i++;
        }

        for (int x = 0; x < koko; x++) {
            for (int y = 0; y < koko; y++) {
                if(y != 0) {
                    System.out.print(" ");
                }
                System.out.print(lauta.getOrDefault(new Coords(x, y), 0));
            }

            System.out.print("\n");
        }
    }
}

Test 1

Group: 1, 2, 3

Verdict: ACCEPTED

Test 2

Group: 1, 2, 3

Verdict: ACCEPTED

Test 3

Group: 1, 2, 3

Verdict: ACCEPTED

Test 4

Group: 1, 2, 3

Verdict: ACCEPTED

Test 5

Group: 1, 2, 3

Verdict: ACCEPTED

Test 6

Group: 1, 2, 3

Verdict: ACCEPTED

Test 7

Group: 1, 2, 3

Verdict: ACCEPTED

Test 8

Group: 2, 3

Verdict: ACCEPTED

Test 9

Group: 2, 3

Verdict: ACCEPTED

Test 10

Group: 2, 3

Verdict: ACCEPTED

Test 11

Group: 3

Verdict: ACCEPTED

Test 12

Group: 3

Verdict: ACCEPTED

Test 13

Group: 3

Verdict: ACCEPTED