MazeRecursion.java

package com.thealgorithms.backtracking;

public class MazeRecursion {

	public static void mazeRecursion() {
		// First create a 2 dimensions array to mimic a maze map
		int[][] map = new int[8][7];
		int[][] map2 = new int[8][7];

		// We use 1 to indicate wall
		// Set the ceiling and floor to 1
		for (int i = 0; i < 7; i++) {
			map[0][i] = 1;
			map[7][i] = 1;
		}

		// Then we set the left and right wall to 1
		for (int i = 0; i < 8; i++) {
			map[i][0] = 1;
			map[i][6] = 1;
		}

		// Now we have created a maze with its wall initialized

		// Here we set the obstacle
		map[3][1] = 1;
		map[3][2] = 1;

		// Print the current map
		System.out.println("The condition of the map： ");
		for (int i = 0; i < 8; i++) {
			for (int j = 0; j < 7; j++) {
				System.out.print(map[i][j] + " ");
			}
			System.out.println();
		}

		// clone another map for setWay2 method
		for (int i = 0; i < map.length; i++) {
			for (int j = 0; j < map[i].length; j++) {
				map2[i][j] = map[i][j];
			}
		}

		// By using recursive backtracking to let your ball(target) find its way in the
		// maze
		// The first parameter is the map
		// Second parameter is x coordinate of your target
		// Thrid parameter is the y coordinate of your target
		setWay(map, 1, 1);
		setWay2(map2, 1, 1);

		// Print out the new map1, with the ball footprint
		System.out.println("After the ball goes through the map1，show the current map1 condition");
		for (int i = 0; i < 8; i++) {
			for (int j = 0; j < 7; j++) {
				System.out.print(map[i][j] + " ");
			}
			System.out.println();
		}

		// Print out the new map2, with the ball footprint
		System.out.println("After the ball goes through the map2，show the current map2 condition");
		for (int i = 0; i < 8; i++) {
			for (int j = 0; j < 7; j++) {
				System.out.print(map2[i][j] + " ");
			}
			System.out.println();
		}
	}



	// Using recursive path finding to help the ball find its way in the maze
	// Description：
	// 1. map (means the maze)
	// 2. i, j (means the initial coordinate of the ball in the maze)
	// 3. if the ball can reach the end of maze, that is position of map[6][5],
	// means the we have found a path for the ball
	// 4. Additional Information： 0 in the map[i][j] means the ball has not gone
	// through this position, 1 means the wall, 2 means the path is feasible, 3
	// means the ball has gone through the path but this path is dead end
	// 5. We will need strategy for the ball to pass through the maze for example:
	// Down -> Right -> Up -> Left, if the path doesn't work, then backtrack
	/**
	 *
	 * @Description
	 * @author OngLipWei
	 * @date Jun 23, 202111:36:14 AM
	 * @param map The maze
	 * @param i x coordinate of your ball(target)
	 * @param j y coordinate of your ball(target)
	 * @return If we did find a path for the ball，return true，else false
	 */
	public static boolean setWay(int[][] map, int i, int j) {
		if (map[6][5] == 2) {// means the ball find its path, ending condition
			return true;
		}
		if (map[i][j] == 0) { // if the ball haven't gone through this point
			// then the ball follows the move strategy : down -> right -> up -> left
			map[i][j] = 2; // we assume that this path is feasible first, set the current point to 2 first。
			if (setWay(map, i + 1, j)) { // go down
				return true;
			} else if (setWay(map, i, j + 1)) { // go right
				return true;
			} else if (setWay(map, i - 1, j)) { // go up
				return true;
			} else if (setWay(map, i, j - 1)) { // go left
				return true;
			} else {
				// means that the current point is the dead end, the ball cannot proceed, set
				// the current point to 3 and return false, the backtraking will start, it will
				// go to the previous step and check for feasible path again
				map[i][j] = 3;
				return false;
			}

		} else { // if the map[i][j] != 0 , it will probably be 1,2,3, return false because the
			// ball cannot hit the wall, cannot go to the path that has gone though before,
			// and cannot head to deadend.
			return false;
		}

	}

	// Here is another move strategy for the ball: up->right->down->left
	public static boolean setWay2(int[][] map, int i, int j) {
		if (map[6][5] == 2) {// means the ball find its path, ending condition
			return true;
		}
		if (map[i][j] == 0) { // if the ball haven't gone through this point
			// then the ball follows the move strategy : up->right->down->left
			map[i][j] = 2; // we assume that this path is feasible first, set the current point to 2 first。
			if (setWay2(map, i - 1, j)) { // go up
				return true;
			} else if (setWay2(map, i, j + 1)) { // go right
				return true;
			} else if (setWay2(map, i + 1, j)) { // go down
				return true;
			} else if (setWay2(map, i, j - 1)) { // go left
				return true;
			} else {
				// means that the current point is the dead end, the ball cannot proceed, set
				// the current point to 3 and return false, the backtraking will start, it will
				// go to the previous step and check for feasible path again
				map[i][j] = 3;
				return false;
			}

		} else { // if the map[i][j] != 0 , it will probably be 1,2,3, return false because the
			// ball cannot hit the wall, cannot go to the path that has gone though before,
			// and cannot head to deadend.
			return false;
		}

	}

}