My HackeRank.com BotClean solution. https://www.hackerrank.com/challenges/botclean

Solutoion.java

import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    public static List<List<Integer>> getDirtyPositions(String[] board) {
        List<List<Integer>> dirtyPositions = new ArrayList<List<Integer>>();
        for (int i=0; i < 5; i++) {
            String line = board[i];
            for (int j=0; j < 5; j++) {
                char square = line.charAt(j);

                if ((int) square == 100) {
                    List<Integer> newDirtyPosition = new ArrayList<Integer>();
                    newDirtyPosition.add(j);
                    newDirtyPosition.add(i);
                    dirtyPositions.add(newDirtyPosition);
                    System.err.println("d @ ("+j+","+i+")");
                }
            }
        }
        return dirtyPositions;
    } 
    
    public static int distanceTo(int fromX, int fromY, List<Integer> target) {
        return (int) Math.sqrt((Math.pow(target.get(0) - fromX, 2) + Math.pow(target.get(1) - fromY,2)));
    }
    
    public static List<Integer> getClosestDirtyOne(int fromX, int fromY, List<List<Integer>> dirtyOnes) {
        List<Integer> result = null;
        int shortestDistance = Integer.MAX_VALUE;
        
        for (List<Integer> dirtyOne : dirtyOnes) {
            int currentDistance = distanceTo(fromX, fromY, dirtyOne);            
            
            if (currentDistance < shortestDistance) {
              result = dirtyOne;
              shortestDistance = currentDistance;
                if (shortestDistance <= 1) {
                    break;
                }
            }
        }
        
        return result;
    }
    
    static void printBoard(String[] board) {
        for (int i=0; i < 5; i++) {
            System.err.println(board[i]);
        }
        System.err.println("-----\n");
    }
    
    static void printDirtyOnes(List<List<Integer>> dirtyOnes) {
        for (List<Integer> xy : dirtyOnes) {
            System.err.print("("+xy.get(0)+","+xy.get(1)+"), ");
        }
    }
    
    static void removeDirtyPosition(List<Integer> toRemove, List<List<Integer>> dirtyPositions) {
        Iterator<List<Integer>> iterator = dirtyPositions.iterator();
        while (iterator.hasNext()) {
            List<Integer> position = iterator.next();
            if (position.get(0) == toRemove.get(0) &&
                position.get(1) == toRemove.get(1)) {
                iterator.remove();
                return;
            }
        }
    }

    
    /* Head ends here */
    static void next_move(int posx, int posy, String[] board){
        //add logic here
        List<List<Integer>> dirtyPositions = getDirtyPositions(board);
        
        //while (dirtyPositions.size() > 0) { //leave this if you want to test in one run
        if(dirtyPositions.size() > 0) {
           List<Integer> closestDirtyOne = getClosestDirtyOne(posx, posy, dirtyPositions);
           int dirtX = closestDirtyOne.get(0);
           int dirtY = closestDirtyOne.get(1);
           int deltaX = dirtX - posx;
           int deltaY = dirtY - posy;
           int newX = 0;
           int newY = 0;
           
           System.err.println("Me ("+posx+","+posy+") - Dirt ("+dirtX+","+dirtY+")");
           System.err.println("Cuadratic Distance: " + distanceTo(posx,posy,closestDirtyOne));
            
           String output = null;
           if (deltaX == 0 && deltaY == 0) {
               output = "CLEAN";
               newX = dirtX;
               newY =dirtY;
               removeDirtyPosition(closestDirtyOne, dirtyPositions);
           } else {
               if (deltaX > 0) {
                   output = "RIGHT";
                   newX = posx + 1;
                   newY = posy;
               } else if (deltaY > 0) {
                   output = "DOWN";
                   newY = posy + 1;
                   newX = posx;
               } else if (deltaX < 0) {
                   output = "LEFT";
                   newX = posx - 1;
                   newY = posy;
               } else if (deltaY < 0) {
                   output = "UP";
                   newY = posy - 1;
                   newX = posx;
               }
           }

           //update board state in memory if testing with while block.
           //System.out.println(output);
           //System.err.println("\nBoard before move ["+output+"]");
           //printBoard(board);
           //char[] line = board[posy].toCharArray();
           //line[posx] = '-';
           //board[posy] = new String(line);
           
           //line = board[newY].toCharArray();
           //line[newX] = 'b';
           //board[newY] = new String(line);

           System.out.println(output);
           //System.err.println("Board after move:");
           //printBoard(board);
           //printDirtyOnes(dirtyPositions);
           //System.err.println("=========================================\n\n");
           
           //posx = newX;
           //posy = newY;
        }
    }

/* Tail starts here */
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int [] pos = new int[2];
        String board[] = new String[5];
        for(int i=0;i<2;i++) pos[i] = in.nextInt();
        for(int i=0;i<5;i++) board[i] = in.next();
        next_move(pos[0], pos[1], board);
    }
}