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class BFS {
// queue of coordinates.
static Coordinates[] queue = new Coordinates[1000];
private static int front = -1;
private static int rear = -1;
static void enqueue(Coordinates coord) {
if (front == -1 && rear == -1) {
front = 0;
rear = 0;
} else {
rear++;
}
queue[rear] = coord;
}
static void dequeue() {
if (front == rear) {
front = -1;
rear = -1;
} else {
front++;
}
}
// traversing directions.
private static final int[][] dir = new int[][]{
{+0, +1}, // right.
{+1, +0}, // down.
{+0, -1}, // left.
{-1, +0}, // up.
};
static void bfs(char[][] maze, Coordinates start, boolean[][] visited,Coordinates [][] path) {
for (int i = 0; i < 4; i++) {
int curx = start.x;
int cury = start.y;
curx += dir[i][0];
cury += dir[i][1];
if (curx < 0 || cury < 0 || curx > maze.length - 1 || cury > maze.length - 1) {
// for square... out of maze check.
continue;
}
// Print the maze on every iteration.
for(int j = 0; j < maze.length; j++)
for(int k = 0; k < maze[j].length; k++) {
if (maze[j][k] == '^' || maze[j][k] == '$')
System.out.print(maze[j][k]);
else {
if (j == curx && k == cury)
System.out.print("@");
else {
if (visited[j][k])
System.out.print("-");
else
System.out.print(maze[j][k]);
}
}
}
System.out.println();
if (maze[curx][cury] == '$') {
path[curx][cury]=new Coordinates(start.x,start.y);
boolean[][] printpath=new boolean[maze.length][maze.length];
for (int q = 0; q < maze.length; q++) {
for (int j = 0; j < maze.length; j++) {
printpath[q][j]=false;
}
}
printpath[0][0]=true; //start as true
while(curx != 0 || cury != 0){
printpath[curx][cury] = true;
int temp = curx;
curx = path[curx][cury].x;
cury = path[temp][cury].y;
//path stores parent of current coordinate
}
for(int j = 0; j < maze.length; j++)
for(int k = 0; k < maze[j].length; k++) {
if (maze[j][k] == '^' || maze[j][k] == '$')
System.out.print(maze[j][k]);
else {
if (j == curx && k == cury)
System.out.print("@");
else {
if(printpath[j][k])
System.out.print("~");
else if (visited[j][k])
System.out.print("-");
else
System.out.print(maze[j][k]);
}
}
}
System.out.println();
System.exit(0);
} else if (visited[curx][cury] || maze[curx][cury] == '#') {
continue;
} else if(maze[curx][cury]=='.') {
enqueue(new Coordinates(curx, cury));
visited[curx][cury] = true;
path[curx][cury]=new Coordinates(start.x,start.y);
}
}
dequeue();
if (front == -1) {
System.out.println("path not found");
System.exit(0);
} else{
// System.out.println(start.x + " " + start.y);
bfs(maze, queue[front], visited, path);
}
}
public static void main(String[] args) {
char[][] maze = {
{'^', '#', '.'},
{'.', '.', '#'},
{'.', '.', '$'},
};
Coordinates start = new Coordinates(0,0);
boolean[][] visited = new boolean[maze.length][maze.length];
Coordinates[][] path = new Coordinates[maze.length][maze.length];
for (int i = 0; i < maze.length; i++) {
for (int j = 0; j < maze.length; j++) {
visited[i][j] = false;
path[i][j] = new Coordinates(0, 0);
}
}
visited[0][0] = true;
enqueue(start);
bfs(maze, start, visited,path);
}
}
class Coordinates {
// for storing coordinates as object.
public int x, y;
Coordinates(int x,int y) {
this.x = x;
this.y = y;
}
}
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