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| package airbnb;
import java.util.Random;
public class TileBoard {
int[][] board;
int[][] visited;
int x;
int y;
public TileBoard() {
board = new int[3][3];
int start = 1;
for (int i = 0; i < 3; i++) {
for (int j = 0; j < 3; j++) {
if (start >= 9) {
break;
}
board[i][j] = start++;
}
}
x = 2;
y = 2;
visited = new int[3][3];
}
public void shuffle() {
Random random = new Random();
int moves = random.nextInt(5);
while (moves > 0) {
int dir = random.nextInt(4);
try {
slide(Direction.values()[dir], 0, false);
moves--;
} catch (RuntimeException e) {
}
}
System.out.println("finished shuffle");
}
public boolean sovle() {
return solveHelper(1, 0);
}
public boolean solveHelper(int level, int moves) {
if (x == 2 && y == 2) {
if (moves == 1) {
System.out.println("back to 2,2");
}
return finalCheck();
} else if (moves >= 8) {
return false;
} else {
int oldX = x;
int oldY = y;
for (Direction dir : Direction.values()) {
visited[oldX][oldY] = 1;
try {
slide(dir, level, false);
System.out.println(toString());
} catch (RuntimeException e) {
continue;
}
if (solveHelper(level + 1, moves + 1)) {
return true;
} else {
try {
Direction back = reverse(dir);
System.out.println("reversing " + back.toString());
slide(back, level, true);
System.out.println(toString());
} catch (RuntimeException e) {
}
}
}
return false;
}
}
public Direction reverse(Direction dir) {
switch (dir) {
case Up:
return Direction.down;
case down:
return Direction.Up;
case left:
return Direction.right;
case right:
return Direction.left;
}
return null;
}
public boolean finalCheck() {
int start = 1;
for (int i = 0; i < 3; i++) {
for (int j = 0; j < 3; j++) {
if (start > 8) {
break;
}
if (board[i][j] != start++) {
return false;
}
}
}
return true;
}
public void slide(Direction direction, int level, boolean reverse) {
int newY = y;
int newX = x;
switch (direction) {
case Up:
newX = x - 1;
if (newX < 0) {
throw new RuntimeException();
}
break;
case down:
newX = x + 1;
if (newX > 2) {
throw new RuntimeException();
}
break;
case left:
newY = y - 1;
if (newY < 0) {
throw new RuntimeException();
}
break;
case right:
newY = y + 1;
if (newY > 2) {
throw new RuntimeException();
}
break;
}
if (reverse) {
visited[newX][newY] = 0;
}
if (visited[newX][newY] == 0) {
int target = board[newX][newY];
board[x][y] = target;
board[newX][newY] = 0;
x = newX;
y = newY;
System.out.println(level + " slide " + direction.toString() + " to x " + x + " y " + y);
} else {
throw new RuntimeException();
}
}
public enum Direction {
Up, down, left, right
}
public static void main(String[] args) {
TileBoard interview = new TileBoard();
System.out.println(interview.toString());
interview.shuffle();
System.out.println(interview.toString());
interview.sovle();
System.out.println(interview.toString());
System.out.println(interview.finalCheck());
}
@Override
public String toString() {
StringBuilder sb = new StringBuilder();
for (int i = 0; i < 3; i++) {
if (i > 0) {
sb.append("\n");
}
for (int j = 0; j < 3; j++) {
sb.append(board[i][j] + " ");
}
}
return sb.toString();
}
}
|