Team Teach Homework

Maze Solver Problem

Instructions

Your task is to write a method solveMaze(char[][] maze, int startX, int startY) that determines whether a path exists from a starting point (startX, startY) in a 2D maze to the exit marked as 'E'. Use recursion to explore the maze.

Requirements

Input

• A 2D array of characters (char[][] maze) representing the maze.

• An integer startX indicating the row index of the starting point.

• An integer startY indicating the column index of the starting point.

Output

• Return true if there is a path from (startX, startY) to 'E'.

• Return false if no such path exists.

Maze Rules

• ' ' represents an open path (you can move here).

• '#' represents a wall (you cannot move here).

• 'E' represents the exit (this is the destination).

Movement

• You can move up, down, left, or right to adjacent cells.

• You cannot move diagonally or leave the bounds of the maze.

Marking Visited Cells

• To avoid revisiting the same cells, mark visited cells as '#' temporarily during recursion. Restore them to ' ' after backtracking.

Steps to Solve

1. Check if the current position is valid:

   • Is it within the bounds of the maze?

   • Is it an open path or the exit?

2. Check if the current position is 'E'. If yes, return true.

3. Mark the current cell as visited (change it to '#').

4. Recursively explore all possible directions (up, down, left, right).

5. If any direction leads to the exit, return true.

6. Restore the cell to ' ' after exploring (backtracking).

7. If no paths lead to the exit, return false.

//Test Case 2: Starting at the Exit


char[][] maze = {
    {'#', '#', '#', '#', '#'},
    {'#', ' ', ' ', '#', 'E'},
    {'#', ' ', '#', ' ', '#'},
    {'#', ' ', ' ', ' ', '#'},
    {'#', '#', '#', '#', '#'}
};

System.out.println(solveMaze(maze, 1, 4)); // Output: true

public class MazeSolver {
    
    public static boolean solveMaze(char[][] maze, int x, int y) {
        if (!valid(maze, x, y)) {
            return false;
        }
        if (maze[x][y] == 'E') {
            return true;
        }

        maze[x][y] = '#';

        if (solveMaze(maze, x - 1, y) || 
            solveMaze(maze, x + 1, y) ||
            solveMaze(maze, x, y - 1) || 
            solveMaze(maze, x, y + 1)) { 
            return true;
        }

        maze[x][y] = ' ';

        return false;
    }

    private static boolean valid(char[][] maze, int x, int y) {
        return x >= 0 && x < maze.length && 
               y >= 0 && y < maze[0].length && 
               (maze[x][y] == ' ' || maze[x][y] == 'E'); 
    }

    }

MazeSolver solver = new MazeSolver();
char[][] maze = {
    { '#', '#', '#', '#', '#' },
    { '#', ' ', ' ', ' ', 'E' },
    { '#', ' ', '#', ' ', '#' },
    { '#', ' ', ' ', ' ', '#' },
    { '#', '#', '#', '#', '#' }
};
System.out.println(solver.solveMaze(maze, 1, 1)); // Output: true
    

true