usaco why did the cow cross the road iii silver java code example

Example: usaco why did the cow cross the road iii silver java

//sample input
3 3 3
2 2 2 3
3 3 3 2
3 3 2 3
3 3
2 2
2 3
//CODE (2021/1/18) YY/MM/DD
  import java.util.*;
import java.io.*;
public class Main {
    static  field[][] farm;
  public static void main(String[] args) throws Exception {
    Scanner sc = new Scanner (new File("countcross.in"));
    int n = sc.nextInt();//n x n grid
    int k = sc.nextInt();// k cows
    int r = sc.nextInt();// r roads
     farm = new field[n][n];
    for (int i = 0; i < n; i++) Arrays.fill(farm[i], new field());
    for (int i = 0; i < r; i++) setRoad(new position(sc.nextInt(), sc.nextInt()), 
                                        new position(sc.nextInt(), sc.nextInt()));
    //floodFill
    int no1 = 0;
    for (int x = 0; x < n; x++ ){
        for (int y = 0; y < n; y++){
            if (!farm[x][y].visited){
                floodFill(x, y, farm[x][y], no1);
                no1++;
            }
        }
    }
    no1--;
    int[] cows = new int[no1];
    
    for (int i = 0; i < k; i++){
        int x = sc.nextInt();
        int y = sc.nextInt();
        int index = farm[x-1][y-1].fieldNum;
        cows[index - 1]++;
    }
    int answer = 0; 
    for (int i = 1; i < cows.length; i++){// when i = 0, it is in the default group, which means that it requires no road.
        answer += k - cows[i];
    }
    PrintWriter out = new PrintWriter(new File("countcross.out"));
    out.println(answer);
    out.close();
    sc.close();
  }
  static void floodFill(int x, int y, field thisF, int no1){
      if (x < 0 || y < 0 || x >= farm.length || y >= farm[0].length) return; // Out of bound
      if (thisF.visited) return; //visited
      thisF = farm[x][y];
      thisF.visited = true;
      thisF.fieldNum = no1;
      if (!thisF.fence[field.north]) floodFill(x, y+1, farm[x][y], no1);
      if (!thisF.fence[field.south]) floodFill(x, y-1, farm[x][y], no1);
      if (!thisF.fence[field.east]) floodFill(x+1, y, farm[x][y], no1);
      if (!thisF.fence[field.west]) floodFill(x-1, y, farm[x][y], no1);
  }
  static void setRoad(position from, position to){
      int dirF = from.pointTo(to);
      int dirT = to.pointTo(from);
      farm[from.x - 1][from.y - 1].fence[dirF] = true;
      farm[to.x - 1][to.y - 1].fence[dirT] = true;
  }
}
class field {
    public boolean visited = false;
    public int fieldNum = -1;
    public boolean[] fence = new boolean[4];//NSWE
    public field(){

    }
   static final int north = 0;
   static final int south = 1;
   static final int west = 2;
   static final int east = 3;
}
class position {
    public int x;
    public int y;
    public position(int x, int y){
        this.x = x;
        this.y = y;
    }
    public int pointTo(position a){
        if (a.x > this.x) return field.east; if (a.x < this.x) return field.west;//x
        if (a.y > this.y) return field.north; if (a.y < this.y) return field.south;//y
        System.out.println("ERROR: poinTo");
        return -1;
    
    }
}
//Output:
     2