(UVA) Maze Exploration - Solution

I used Depth-First Search to solve this problem.


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

class Main  {
    public static char[][] matrix;
    public static int[] vx = {-1,1,0,0};
    public static int[] vy = {0,0,1,-1};
   
    public static void dfs(int currX, int currY, int numRows, int numCols) {
        if (currX < 0 || currY < 0 || currX >= numRows || currY >= numCols || matrix[currX][currY] == '#' || (matrix[currX][currY] != ' ' && matrix[currX][currY] != '*')) {
            return;
        }

        matrix[currX][currY] = '#';
        for (int i = 0; i < 4; i++) {
            int nextX = currX+vx[i];
            int nextY = currY+vy[i];

            dfs(nextX, nextY, numRows, numCols);
        }
    }
   
    public static void process() throws NumberFormatException, IOException {  
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
       
        String line = br.readLine();
        int numCases = Integer.parseInt(line);
        for (int i = 0; i < numCases; i++) {
            ArrayList<String> strings = new ArrayList<String>();
            line = br.readLine();
            while (line.charAt(0) != '_') {
                strings.add(line);
                line = br.readLine();
            }
            String separate = line;
           
            int maxLength = 0;
            for (int j = 0; j < strings.size(); j++) {
                if (strings.get(j).length() > maxLength) {
                    maxLength = strings.get(j).length();
                }
            }
           
            int x = -1;
            int y = -1;
            matrix = new char[strings.size()][maxLength];
            for (int j = 0; j < strings.size(); j++) {
                for (int k = 0; k < strings.get(j).length(); k++) {
                    matrix[j][k] = strings.get(j).charAt(k);
                    if (strings.get(j).charAt(k) == '*') {
                        x = j;
                        y = k;
                    }
                }
            }
           
            dfs(x, y, strings.size(), maxLength);
           
            for (int j = 0; j < strings.size(); j++) {
                for (int k = 0; k < strings.get(j).length(); k++) {
                    System.out.print(matrix[j][k]);
                }
                System.out.println();
            }
            System.out.println(separate);
        }    
                                            
        return;
    }
  
    public static void main(String[] args) throws NumberFormatException, IOException {
        Main m = new Main();
        m.process();

        System.exit(0);
    }
}