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Bael 1299 - Maze Solver - deep20jain@gmail.com (#3537) 

* Maze solver using DFS

* Adding BFS maze solver

* Fixing formatting
This commit is contained in:
deep20jain 2018-02-07 01:37:38 +05:30 committed by Grzegorz Piwowarek
parent 5a34de448e
commit efb66e3001
7 changed files with 340 additions and 0 deletions
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52
algorithms/src/main/java/com/baeldung/algorithms/maze/solver/BFSMazeSolver.java Normal file
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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<Coordinate> solve(Maze maze) {
LinkedList<Coordinate> 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<Coordinate> backtrackPath(Coordinate cur) {
List<Coordinate> path = new ArrayList<>();
Coordinate iter = cur;
while (iter != null) {
path.add(iter);
iter = iter.parent;
}
return path;
}
}

31
algorithms/src/main/java/com/baeldung/algorithms/maze/solver/Coordinate.java Normal file
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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;
}
}

48
algorithms/src/main/java/com/baeldung/algorithms/maze/solver/DFSMazeSolver.java Normal file
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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<Coordinate> solve(Maze maze) {
List<Coordinate> 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<Coordinate> 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);
}
}

141
algorithms/src/main/java/com/baeldung/algorithms/maze/solver/Maze.java Normal file
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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<Coordinate> 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);
}
}

34
algorithms/src/main/java/com/baeldung/algorithms/maze/solver/MazeDriver.java Normal file
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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<Coordinate> path = bfs.solve(maze);
maze.printPath(path);
maze.reset();
}
private static void dfs(Maze maze) {
DFSMazeSolver dfs = new DFSMazeSolver();
List<Coordinate> path = dfs.solve(maze);
maze.printPath(path);
maze.reset();
}
}

12
algorithms/src/main/resources/maze/maze1.txt Normal file
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S ########
# #
# ### ## #
# # # #
# # # # #
# ## #####
# # #
# # # # #
##### ####
# # E
# # # #
##########

22
algorithms/src/main/resources/maze/maze2.txt Normal file
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S ##########################
# # # #
# # #### ############### #
# # # # # #
# # #### # # ###############
# # # # # # #
# # # #### ### ########### #
# # # # # #
# ################## #
######### # # # # #
# # #### # ####### # #
# # ### ### # # # # #
# # ## # ##### # #
##### ####### # # # # #
# # ## ## #### # #
# ##### ####### # #
# # ############
####### ######### # #
# # ######## #
# ####### ###### ## # E
# # # ## #
############################