Created
December 26, 2017 07:20
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Lights Out algorithms challenge - breadth first, can extend to A*
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| public class Bulbs { | |
| public static void main(String[] args) { | |
| Board challenge = new Board(3); | |
| challenge.set(1, 0, true); | |
| System.out.println("CHALLENGE"); | |
| System.out.println(challenge); | |
| System.out.println("SOLUTION"); | |
| Board solution = solve(challenge); | |
| if (solution == null) { | |
| System.out.println("(no solution found)"); | |
| return; | |
| } | |
| Board after = challenge; | |
| for (int i = 0; i < solution.moves.length; i++) { | |
| Point move = solution.moves[i]; | |
| System.out.println("FLIP " + move.x + ", " + move.y); | |
| after = after.toggle(move.x, move.y); | |
| System.out.println(after); | |
| } | |
| } | |
| private static Board solve(Board challenge) { | |
| Queue<Board> q = new LinkedList<>(); | |
| q.add(challenge); | |
| int n = challenge.n; | |
| while (!q.isEmpty()) { | |
| Board current = q.poll(); | |
| for (int i = 0; i < n; i++) { | |
| for (int j = 0; j < n; j++) { | |
| Board next = current.toggle(i, j); | |
| if (next.isClear()) { | |
| return next; | |
| } | |
| q.add(next); | |
| } | |
| } | |
| } | |
| return null; | |
| } | |
| private static class Board { | |
| private final int n; | |
| private final boolean[] board; | |
| private final Point[] moves; | |
| private Board(int n) { | |
| this.n = n; | |
| board = new boolean[n * n]; | |
| moves = new Point[0]; | |
| } | |
| public boolean isClear() { | |
| for (int i = 0; i < n * n; i++) { | |
| if (board[i]) { | |
| return false; | |
| } | |
| } | |
| return true; | |
| } | |
| @Override | |
| public String toString() { | |
| StringBuilder ret = new StringBuilder(); | |
| for (int i = 0; i < n; i++) { | |
| for (int j = 0; j < n; j++) { | |
| ret.append(board[i * n + j] ? "1" : "0"); | |
| } | |
| ret.append('\n'); | |
| } | |
| return ret.toString(); | |
| } | |
| private Board(Board prev, Point move) { | |
| this.n = prev.n; | |
| board = Arrays.copyOf(prev.board, prev.board.length); | |
| moves = Arrays.copyOf(prev.moves, prev.moves.length + 1); | |
| moves[prev.moves.length] = move; | |
| } | |
| private void set(int i, int j, boolean val) { | |
| board[i * n + j] = val; | |
| } | |
| private Board toggle(int i, int j) { | |
| Board ret = new Board(this, new Point(i, j)); | |
| ret.flip(i - 1, j); | |
| ret.flip(i + 1, j); | |
| ret.flip(i, j - 1); | |
| ret.flip(i, j + 1); | |
| ret.flip(i, j); | |
| return ret; | |
| } | |
| private void flip(int i, int j) { | |
| if (i < 0 || j < 0 || i >= n || j >= n) { | |
| return; | |
| } | |
| board[i * n + j] = !board[i * n + j]; | |
| } | |
| } |
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