Ruudukko

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.lang.System;
import java.util.Arrays;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
public class App {
    public static void main()throws Exception{
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        int GridSize = Integer.parseInt(br.readLine());
        int GridSizeSq = GridSize*GridSize;
        int[][] Grid = new int[GridSize][3];
        int[][] SortedGrid = Grid;
 
        int counter = 0;
        for (int i = 0; i < GridSize; i++) {
            int[] NodeStates = Arrays.stream(br.readLine().split(" ")).mapToInt(Integer::parseInt).toArray();
            for (int j : NodeStates) {
                Grid[counter] = new int[]{counter, j, 1};
                counter += 1;
            }
        }
        Arrays.sort(SortedGrid, (a,b)-> Integer.compare(a[0], b[0]));
        int t= 1;
    }
 
}

Test 1

Group: 1, 2, 3

Verdict: RUNTIME ERROR

Error: Main method not found in class App, please define the main method as:
   public sta...

Test 2

Group: 1, 2, 3

Verdict: RUNTIME ERROR

Error: Main method not found in class App, please define the main method as:
   public sta...

Test 3

Group: 1, 2, 3

Verdict: RUNTIME ERROR

Error: Main method not found in class App, please define the main method as:
   public sta...

Test 4

Group: 2, 3

Verdict: RUNTIME ERROR

Error: Main method not found in class App, please define the main method as:
   public sta...

Test 5

Group: 2, 3

Verdict: RUNTIME ERROR

Error: Main method not found in class App, please define the main method as:
   public sta...

Test 6

Group: 2, 3

Verdict: RUNTIME ERROR

Error: Main method not found in class App, please define the main method as:
   public sta...

Test 7

Group: 3

Verdict: RUNTIME ERROR

Error: Main method not found in class App, please define the main method as:
   public sta...

Test 8

Group: 3

Verdict: RUNTIME ERROR

Error: Main method not found in class App, please define the main method as:
   public sta...

Test 9

Group: 3

Verdict: RUNTIME ERROR

Error: Main method not found in class App, please define the main method as:
   public sta...