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Commit 4979945

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solves castle on the grid
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β€ŽREADME.mdβ€Ž

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@@ -121,7 +121,7 @@ I have also solved other domains on HackerRank that can be viewed at:
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| Problem | Difficulty Level | Solution Link |
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|---------|------------------|---------------|
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| [Queue Using Two Stacks](https://www.hackerrank.com/challenges/queue-using-two-stacks) | Medium | [![Java](https://img.icons8.com/color/40/000000/java-coffee-cup-logo.png)](https://github.com/anishLearnsToCode/hackerrank-data-structures/blob/master/src/queues/QueueUsingTwoStacks.java) |
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| [Castle on The Grid](https://www.hackerrank.com/challenges/castle-on-the-grid) | Medium | |
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| [Castle on The Grid](https://www.hackerrank.com/challenges/castle-on-the-grid) | Medium | [![Java](https://img.icons8.com/color/40/000000/java-coffee-cup-logo.png)]()|
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| [Down to Zero II](https://www.hackerrank.com/challenges/down-to-zero-ii) | Medium | |
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| [Truck Hour](https://www.hackerrank.com/challenges/truck-tour) | Hard | |
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| [Queries with Fixed Length](https://www.hackerrank.com/challenges/queries-with-fixed-length) | Hard | |
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// https://www.hackerrank.com/challenges/castle-on-the-grid/problem
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package queues;
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import java.util.HashMap;
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import java.util.LinkedList;
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import java.util.Map;
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import java.util.Objects;
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import java.util.Queue;
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import java.util.Scanner;
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public class CastleOnTheGrid {
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private static final Scanner scanner = new Scanner(System.in);
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public static void main(String[] args) {
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int length = scanner.nextInt();
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String[] grid = getGrid(length);
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int startX = scanner.nextInt();
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int startY = scanner.nextInt();
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int endX = scanner.nextInt();
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int endY = scanner.nextInt();
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Grid solution = new Grid(grid, new Position(startX, startY), new Position(endX, endY));
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System.out.println(solution.shortestPath());
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}
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private static class Position {
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private final int x;
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private final int y;
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Position(int x, int y) {
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this.x = x;
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this.y = y;
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}
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boolean notBlocked(String[] grid) {
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return grid[x].charAt(y) != 'X';
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}
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boolean isValidPosition(String[] grid) {
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return x < grid.length
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&& x >= 0
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&& y < grid[0].length()
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&& y >= 0;
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}
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Position goUp() {
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return new Position(x - 1, y);
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}
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Position goRight() {
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return new Position(x, y + 1);
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}
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Position goDown() {
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return new Position(x + 1, y);
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}
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Position goLeft() {
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return new Position(x, y - 1);
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}
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@Override
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public boolean equals(Object o) {
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if (this == o) return true;
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if (o == null || getClass() != o.getClass()) return false;
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Position position = (Position) o;
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return x == position.x && y == position.y;
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}
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@Override
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public int hashCode() {
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return Objects.hash(x, y);
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}
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@Override
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public String toString() {
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return "(" +
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"" + x +
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", " + y +
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')';
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}
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}
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private static class Grid {
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private final String[] grid;
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private final Position source;
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private final Position destination;
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private final LateralMovement up = new UpLateralMovement();
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private final LateralMovement right = new RightLateralMovement();
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private final LateralMovement down = new DownLateralMovement();
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private final LateralMovement left = new LeftLateralMovement();
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Grid(String[] grid, Position source, Position destination) {
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this.grid = grid;
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this.source = source;
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this.destination = destination;
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}
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int shortestPath() {
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Map<Position, Position> prefixPositions = new HashMap<>();
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prefixPositions.put(source, source);
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Queue<Position> queue = new LinkedList<>();
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queue.add(source);
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while (!queue.isEmpty()) {
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Position top = queue.poll();
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if (top.equals(destination)) {
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break;
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}
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addLateralVerticesToQueue(top, prefixPositions, queue);
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}
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return shortestPath(prefixPositions);
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}
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private abstract class LateralMovement {
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private void addLateralVerticesToQueue(Position position, Map<Position, Position> prefixes, Queue<Position> queue) {
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Position current = position;
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while (current.isValidPosition(grid) && current.notBlocked(grid)) {
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if (!prefixes.containsKey(current)) {
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prefixes.put(current, position);
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queue.add(current);
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}
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current = lateralVertice(current);
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}
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}
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abstract Position lateralVertice(Position position);
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}
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private class UpLateralMovement extends LateralMovement {
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@Override
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Position lateralVertice(Position position) {
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return position.goUp();
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}
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}
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private class RightLateralMovement extends LateralMovement {
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@Override
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Position lateralVertice(Position position) {
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return position.goRight();
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}
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}
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private class DownLateralMovement extends LateralMovement {
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@Override
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Position lateralVertice(Position position) {
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return position.goDown();
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}
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}
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private class LeftLateralMovement extends LateralMovement {
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@Override
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Position lateralVertice(Position position) {
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return position.goLeft();
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}
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}
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private void addLateralVerticesToQueue(Position position, Map<Position, Position> prefixes, Queue<Position> queue) {
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up.addLateralVerticesToQueue(position, prefixes, queue);
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right.addLateralVerticesToQueue(position, prefixes, queue);
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down.addLateralVerticesToQueue(position, prefixes, queue);
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left.addLateralVerticesToQueue(position, prefixes, queue);
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}
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private int shortestPath(Map<Position, Position> prefixPositions) {
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return shortestPath(prefixPositions, this.destination);
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}
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private int shortestPath(Map<Position, Position> prefixPositions, Position position) {
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if (position.equals(this.source)) {
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return 0;
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}
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return 1 + shortestPath(prefixPositions, prefixPositions.get(position));
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}
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}
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private static String[] getGrid(int length) {
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String[] array = new String[length];
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for (int index = 0 ; index < length ; index++) {
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array[index] = scanner.next();
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}
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return array;
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}
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}

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