Castle on the Grid.java

/*
Problem Title: Castle on the Grid
Problem URL: https://www.hackerrank.com/challenges/one-month-preparation-kit-castle-on-the-grid/problem?h_l=interview&playlist_slugs%5B%5D=preparation-kits&playlist_slugs%5B%5D=one-month-preparation-kit&playlist_slugs%5B%5D=one-month-week-four

Max Score: 100
Score: 100
Language: Java
Category: One Month Preparation
*/


class Result {

    public static int minimumMoves(List<String> grid, int startX, int startY,        int goalX, int goalY) {
        
        int n = grid.size();
        XY start = new XY(startX, startY);
        XY end = new XY(goalX, goalY);
        Set<XY> visited = new HashSet<XY>();
        char[][] mat = new char[n][n];
        
        for (int i = 0; i < n; ++i)
            for (int j = 0; j < n; ++j)
                mat[i][j] = grid.get(i).charAt(j);
        
        return minSteps(mat, start, end, visited);
    }
    
    private static int minSteps(char[][] grid, XY curr, XY end, Set<XY> visited) {
        Queue<XY> queue = new LinkedList<XY>();
        queue.add(curr);
        visited.add(curr);

        Queue<Integer> step = new LinkedList<Integer>();
        step.add(0);

        while (!queue.isEmpty()) {
            XY nextXY = queue.remove();
            int hop = step.remove();

            if (nextXY.equals(end)) return hop;

            List<XY> next = getNext(grid, nextXY, visited);
            visited.addAll(next);
            queue.addAll(next);

            for (int i = 0; i < next.size(); i++) {
                step.add(hop + 1);
            }
        }

        return Integer.MAX_VALUE;
    }

    private static List<XY> getNext(char[][] grid, XY curr, Set<XY> visited) {
        List<XY> next = new ArrayList<XY>();

        if (curr.dir == null || curr.dir == Dir.Y) {
            int x = curr.x;
            for (int i = x - 1; i >= 0; i--) {
                if (grid[i][curr.y] == 'X') break;

                final XY xy = new XY(i, curr.y, Dir.X);
                if (!visited.contains(xy)) next.add(xy);
            }

            for (int i = x + 1; i < grid.length; i++) {
                if (grid[i][curr.y] == 'X') break;

                final XY xy = new XY(i, curr.y, Dir.X);
                if (!visited.contains(xy)) next.add(xy);
            }
        }

        if (curr.dir == null || curr.dir == Dir.X) {
            int y = curr.y;

            for (int i = y - 1; i >= 0; i--) {
                if (grid[curr.x][i] == 'X') break;

                final XY xy = new XY(curr.x, i, Dir.Y);
                if (!visited.contains(xy)) next.add(xy);
            }

            for (int i = y + 1; i < grid.length; i++) {
                if (grid[curr.x][i] == 'X') break;

                final XY xy = new XY(curr.x, i, Dir.Y);
                if (!visited.contains(xy)) next.add(xy);
            }
        }

        return next;
    }


    private static class XY {
        int x, y;
        Dir dir;


        public XY(int x, int y) {
            this.x = x;
            this.y = y;
            dir = null;
        }

        public XY(int x, int y, Dir dir) {
            this.x = x;
            this.y = y;
            this.dir = dir;
        }

        @Override
        public boolean equals(Object o) {
            if (this == o) return true;
            if (o == null || getClass() != o.getClass()) return false;
            XY xy = (XY) o;
            return x == xy.x && y == xy.y;

        }

        @Override
        public int hashCode() {
            return 31 * x + y;
        }

        @Override
        public String toString() {
            return "XY{" +
                    "x=" + x +
                    ", y=" + y +
                    ", dir=" + dir +
                    '}';
        }
    }

    private enum Dir {
        X, Y;
    }
    
}