diff --git a/algorithms/src/main/java/com/baeldung/algorithms/maze/solver/BFSMazeSolver.java b/algorithms/src/main/java/com/baeldung/algorithms/maze/solver/BFSMazeSolver.java new file mode 100644 index 0000000000..08972251b8 --- /dev/null +++ b/algorithms/src/main/java/com/baeldung/algorithms/maze/solver/BFSMazeSolver.java @@ -0,0 +1,52 @@ +package com.baeldung.algorithms.maze.solver; + +import java.util.ArrayList; +import java.util.Collections; +import java.util.LinkedList; +import java.util.List; + +public class BFSMazeSolver { + private static final int[][] DIRECTIONS = { { 0, 1 }, { 1, 0 }, { 0, -1 }, { -1, 0 } }; + + public List solve(Maze maze) { + LinkedList nextToVisit = new LinkedList<>(); + Coordinate start = maze.getEntry(); + nextToVisit.add(start); + + while (!nextToVisit.isEmpty()) { + Coordinate cur = nextToVisit.remove(); + + if (!maze.isValidLocation(cur.getX(), cur.getY()) || maze.isExplored(cur.getX(), cur.getY())) { + continue; + } + + if (maze.isWall(cur.getX(), cur.getY())) { + maze.setVisited(cur.getX(), cur.getY(), true); + continue; + } + + if (maze.isExit(cur.getX(), cur.getY())) { + return backtrackPath(cur); + } + + for (int[] direction : DIRECTIONS) { + Coordinate coordinate = new Coordinate(cur.getX() + direction[0], cur.getY() + direction[1], cur); + nextToVisit.add(coordinate); + maze.setVisited(cur.getX(), cur.getY(), true); + } + } + return Collections.emptyList(); + } + + private List backtrackPath(Coordinate cur) { + List path = new ArrayList<>(); + Coordinate iter = cur; + + while (iter != null) { + path.add(iter); + iter = iter.parent; + } + + return path; + } +} diff --git a/algorithms/src/main/java/com/baeldung/algorithms/maze/solver/Coordinate.java b/algorithms/src/main/java/com/baeldung/algorithms/maze/solver/Coordinate.java new file mode 100644 index 0000000000..09b2ced5e6 --- /dev/null +++ b/algorithms/src/main/java/com/baeldung/algorithms/maze/solver/Coordinate.java @@ -0,0 +1,31 @@ +package com.baeldung.algorithms.maze.solver; + +public class Coordinate { + int x; + int y; + Coordinate parent; + + public Coordinate(int x, int y) { + this.x = x; + this.y = y; + this.parent = null; + } + + public Coordinate(int x, int y, Coordinate parent) { + this.x = x; + this.y = y; + this.parent = parent; + } + + int getX() { + return x; + } + + int getY() { + return y; + } + + Coordinate getParent() { + return parent; + } +} diff --git a/algorithms/src/main/java/com/baeldung/algorithms/maze/solver/DFSMazeSolver.java b/algorithms/src/main/java/com/baeldung/algorithms/maze/solver/DFSMazeSolver.java new file mode 100644 index 0000000000..f9640066b9 --- /dev/null +++ b/algorithms/src/main/java/com/baeldung/algorithms/maze/solver/DFSMazeSolver.java @@ -0,0 +1,48 @@ +package com.baeldung.algorithms.maze.solver; + +import java.util.ArrayList; +import java.util.Collections; +import java.util.List; + +public class DFSMazeSolver { + private static final int[][] DIRECTIONS = { { 0, 1 }, { 1, 0 }, { 0, -1 }, { -1, 0 } }; + + public List solve(Maze maze) { + List path = new ArrayList<>(); + if (explore(maze, maze.getEntry() + .getX(), + maze.getEntry() + .getY(), + path)) { + return path; + } + return Collections.emptyList(); + } + + private boolean explore(Maze maze, int row, int col, List path) { + if (!maze.isValidLocation(row, col) || maze.isWall(row, col) || maze.isExplored(row, col)) { + return false; + } + + path.add(new Coordinate(row, col)); + maze.setVisited(row, col, true); + + if (maze.isExit(row, col)) { + return true; + } + + for (int[] direction : DIRECTIONS) { + Coordinate coordinate = getNextCoordinate(row, col, direction[0], direction[1]); + if (explore(maze, coordinate.getX(), coordinate.getY(), path)) { + return true; + } + } + + path.remove(path.size() - 1); + return false; + } + + private Coordinate getNextCoordinate(int row, int col, int i, int j) { + return new Coordinate(row + i, col + j); + } +} diff --git a/algorithms/src/main/java/com/baeldung/algorithms/maze/solver/Maze.java b/algorithms/src/main/java/com/baeldung/algorithms/maze/solver/Maze.java new file mode 100644 index 0000000000..8aaa44d9b1 --- /dev/null +++ b/algorithms/src/main/java/com/baeldung/algorithms/maze/solver/Maze.java @@ -0,0 +1,141 @@ +package com.baeldung.algorithms.maze.solver; + +import java.io.File; +import java.io.FileNotFoundException; +import java.util.Arrays; +import java.util.List; +import java.util.Scanner; + +public class Maze { + private static final int ROAD = 0; + private static final int WALL = 1; + private static final int START = 2; + private static final int EXIT = 3; + private static final int PATH = 4; + + private int[][] maze; + private boolean[][] visited; + private Coordinate start; + private Coordinate end; + + public Maze(File maze) throws FileNotFoundException { + String fileText = ""; + try (Scanner input = new Scanner(maze)) { + while (input.hasNextLine()) { + fileText += input.nextLine() + "\n"; + } + } + initializeMaze(fileText); + } + + private void initializeMaze(String text) { + if (text == null || (text = text.trim()).length() == 0) { + throw new IllegalArgumentException("empty lines data"); + } + + String[] lines = text.split("[\r]?\n"); + maze = new int[lines.length][lines[0].length()]; + visited = new boolean[lines.length][lines[0].length()]; + + for (int row = 0; row < getHeight(); row++) { + if (lines[row].length() != getWidth()) { + throw new IllegalArgumentException("line " + (row + 1) + " wrong length (was " + lines[row].length() + " but should be " + getWidth() + ")"); + } + + for (int col = 0; col < getWidth(); col++) { + if (lines[row].charAt(col) == '#') + maze[row][col] = WALL; + else if (lines[row].charAt(col) == 'S') { + maze[row][col] = START; + start = new Coordinate(row, col); + } else if (lines[row].charAt(col) == 'E') { + maze[row][col] = EXIT; + end = new Coordinate(row, col); + } else + maze[row][col] = ROAD; + } + } + } + + public int getHeight() { + return maze.length; + } + + public int getWidth() { + return maze[0].length; + } + + public Coordinate getEntry() { + return start; + } + + public Coordinate getExit() { + return end; + } + + public boolean isExit(int x, int y) { + return x == end.getX() && y == end.getY(); + } + + public boolean isStart(int x, int y) { + return x == start.getX() && y == start.getY(); + } + + public boolean isExplored(int row, int col) { + return visited[row][col]; + } + + public boolean isWall(int row, int col) { + return maze[row][col] == WALL; + } + + public void setVisited(int row, int col, boolean value) { + visited[row][col] = value; + } + + public boolean isValidLocation(int row, int col) { + if (row < 0 || row >= getHeight() || col < 0 || col >= getWidth()) { + return false; + } + return true; + } + + public void printPath(List path) { + int[][] tempMaze = Arrays.stream(maze) + .map(int[]::clone) + .toArray(int[][]::new); + for (Coordinate coordinate : path) { + if (isStart(coordinate.getX(), coordinate.getY()) || isExit(coordinate.getX(), coordinate.getY())) { + continue; + } + tempMaze[coordinate.getX()][coordinate.getY()] = PATH; + } + System.out.println(toString(tempMaze)); + } + + public String toString(int[][] maze) { + StringBuilder result = new StringBuilder(getWidth() * (getHeight() + 1)); + for (int row = 0; row < getHeight(); row++) { + for (int col = 0; col < getWidth(); col++) { + if (maze[row][col] == ROAD) { + result.append(' '); + } else if (maze[row][col] == WALL) { + result.append('#'); + } else if (maze[row][col] == START) { + result.append('S'); + } else if (maze[row][col] == EXIT) { + result.append('E'); + } else { + result.append('.'); + } + } + result.append('\n'); + } + return result.toString(); + } + + public void reset() { + for (int i = 0; i < visited.length; i++) + Arrays.fill(visited[i], false); + } +} diff --git a/algorithms/src/main/java/com/baeldung/algorithms/maze/solver/MazeDriver.java b/algorithms/src/main/java/com/baeldung/algorithms/maze/solver/MazeDriver.java new file mode 100644 index 0000000000..60263deba3 --- /dev/null +++ b/algorithms/src/main/java/com/baeldung/algorithms/maze/solver/MazeDriver.java @@ -0,0 +1,34 @@ +package com.baeldung.algorithms.maze.solver; + +import java.io.File; +import java.util.List; + +public class MazeDriver { + public static void main(String[] args) throws Exception { + File maze1 = new File("src/main/resources/maze/maze1.txt"); + File maze2 = new File("src/main/resources/maze/maze2.txt"); + + execute(maze1); + execute(maze2); + } + + private static void execute(File file) throws Exception { + Maze maze = new Maze(file); + dfs(maze); + bfs(maze); + } + + private static void bfs(Maze maze) { + BFSMazeSolver bfs = new BFSMazeSolver(); + List path = bfs.solve(maze); + maze.printPath(path); + maze.reset(); + } + + private static void dfs(Maze maze) { + DFSMazeSolver dfs = new DFSMazeSolver(); + List path = dfs.solve(maze); + maze.printPath(path); + maze.reset(); + } +} diff --git a/algorithms/src/main/resources/maze/maze1.txt b/algorithms/src/main/resources/maze/maze1.txt new file mode 100644 index 0000000000..0a6309d25b --- /dev/null +++ b/algorithms/src/main/resources/maze/maze1.txt @@ -0,0 +1,12 @@ +S ######## +# # +# ### ## # +# # # # +# # # # # +# ## ##### +# # # +# # # # # +##### #### +# # E +# # # # +########## \ No newline at end of file diff --git a/algorithms/src/main/resources/maze/maze2.txt b/algorithms/src/main/resources/maze/maze2.txt new file mode 100644 index 0000000000..22e6d0382a --- /dev/null +++ b/algorithms/src/main/resources/maze/maze2.txt @@ -0,0 +1,22 @@ +S ########################## +# # # # +# # #### ############### # +# # # # # # +# # #### # # ############### +# # # # # # # +# # # #### ### ########### # +# # # # # # +# ################## # +######### # # # # # +# # #### # ####### # # +# # ### ### # # # # # +# # ## # ##### # # +##### ####### # # # # # +# # ## ## #### # # +# ##### ####### # # +# # ############ +####### ######### # # +# # ######## # +# ####### ###### ## # E +# # # ## # +############################ \ No newline at end of file