APCS/02 Recursion/04 AreaFill/AreaFill.java

// Name: B6-24
// Date: 10/02/19

import java.util.*;
import java.io.*;

public class AreaFill
{
   private static char[][] grid = null;
   private static String filename = null;

   public static void main(String[] args) 
   {
      Scanner sc = new Scanner(System.in);
      while(true)  // what does this do?
      {
         System.out.print("Fill the Area of (-1 to exit): ");
         filename = sc.next();
         if(filename.equals("-1"))
         {
            sc.close();
            System.out.println("Good-bye");
            //System.exit(0); 
            return;  
         }
         grid = read(filename);
         String theGrid = display(grid);
         System.out.println( theGrid );
         System.out.print( "1-Fill or 2-Fill-and-Count: ");
         int choice = sc.nextInt();
         switch(choice)
         {
            case 1:
               {
                  System.out.print("\nEnter ROW COL to fill from: ");
                  int row = sc.nextInt();
                  int col = sc.nextInt(); 
                  fill(grid, row, col, grid[row][col]);
                  System.out.println( display(grid) );
                  break;
               }
            case 2:
               {
                  System.out.print("\nEnter ROW COL to fill from: ");
                  int row = sc.nextInt();
                  int col = sc.nextInt();
                  int count = fillAndCount(grid, row, col, grid[row][col]);
                  System.out.println( display(grid) );
                  System.out.println("count = " + count);
                  System.out.println();
                  break;
               }
            default:
               System.out.print("\nTry again! ");
         }
      }
   }
   
   /**
    * Reads the contents of the file into a matrix.
    * Uses try-catch.
    * @param filename The string representing the filename.
    * @returns A 2D array of chars.
    */
   public static char[][] read(String filename)
   {
      Scanner infile = null;
      try
      {
         infile = new Scanner(new File(filename));
      }
      catch (Exception e)
      {
         System.out.println("File not found");
         return null;
      }
      /* enter your code here */
      
      int r = infile.nextInt();
      int c = infile.nextInt();
      char[][] g = new char[r][c];
      infile.nextLine();
      
      for (int i = 0; i < r; i++)
        g[i] = infile.nextLine().toCharArray();
      
      return g;
  }
   
   /**
    * @param g A 2-D array of chars.
    * @returns A string representing the 2D array.
    */
   public static String display(char[][] g)
   {
      String outString = "";
      for (int i = 0; i < g.length; i++){
        for (int j = 0; j < g[i].length; j++){
            outString += g[i][j];
        }
        
        outString += '\n';
      }
      
      return outString;
   }
   
   /**
    * Fills part of the matrix with a different character.
    * @param g A 2D char array.
    * @param r An int representing the row of the cell to be filled.
    * @param c An int representing the column of the cell to be filled.
    * @param ch A char representing the replacement character.
    */
   public static void fill(char[][] g, int r, int c, char ch)
   {
      if(r >= 0 && r < g.length && c >= 0 && c < g[0].length) {     
        if(g[r][c] == ch) {
            g[r][c] = '*';
            fill(g, r + 1, c, ch);
            fill(g, r - 1, c, ch);
            fill(g, r, c + 1, ch);
            fill(g, r, c - 1, ch);
        }
      }
   
      return;
   }
   
   /**
    * Fills part of the matrix with a different character.
    * Counts as you go.  Does not use a static variable.
    * @param g A 2D char array.
    * @param r An int representing the row of the cell to be filled.
    * @param c An int representing the column of the cell to be filled.
    * @param ch A char representing the replacement character.
    * @return An int representing the number of characters that were replaced.
    */
   public static int fillAndCount(char[][] g, int r, int c, char ch)
   {
      if(r >= 0 && r < g.length && c >= 0 && c < g[0].length) {     
        if(g[r][c] == ch) {
            g[r][c] = '*';
            return 1 + fillAndCount(g, r + 1, c, ch) + fillAndCount(g, r - 1, c, ch) + fillAndCount(g, r, c + 1, ch) + fillAndCount(g, r, c - 1, ch);
        }
      }
      
      return 0; //never reached
   }
}