[ADSx] - Board (Simple)

import java.util.*;
import java.util.stream.IntStream;

public class Board {

    public static void main(String args[]) {
        String text = "100 100\n" +
                "2 100 50 50";
        text = "3 3\n" +
                "1 1 3 3";
        //Scanner scanner = new Scanner(text);
        Scanner scanner = new Scanner(System.in);
        int rows = scanner.nextInt();
        int columns = scanner.nextInt();
        scanner.nextLine();

        // Minus one for all because we iterate starting from 0
        int x1 = scanner.nextInt() - 1;
        int y1 = scanner.nextInt() - 1;
        int x2 = scanner.nextInt() - 1;
        int y2 = scanner.nextInt() - 1;

        /**
         * https://en.wikipedia.org/wiki/Knight%27s_graph
         * https://www.geeksforgeeks.org/minimum-steps-reach-target-knight/
         * */

        Integer elements[] = new Integer[(rows + 1) * (columns + 1)];
        IntStream.range(0, elements.length).forEach(i -> elements[i] = i);

        //System.out.print(Arrays.toString(elements));

        Graph<Integer> graph = new Graph<>((rows + 1) * (columns + 1), elements);

        for (int i = 0; i < rows; i++) {
            for (int j = 0; j < columns; j++) {
                if (i + 2 < rows&&j + 1 < columns) {
                    graph.addEdge(transform(i, j, columns), transform(i + 2, j + 1, columns));
                }
                if (i + 2 < rows && j - 1 >= 0) {
                    graph.addEdge(transform(i, j, columns), transform(i + 2, j - 1, columns));
                }
                if (i - 2 >= 0 && j + 1 < columns) {
                    graph.addEdge(transform(i, j, columns), transform(i - 2, j + 1, columns));
                }
                if (i - 2 >= 0 && j - 1 >= 0) {
                    graph.addEdge(transform(i, j, columns), transform(i - 2, j - 1, columns));
                }
                if (j + 2 < columns && i + 1 < rows) {
                    graph.addEdge(transform(i, j, columns), transform(j + 2, i + 1, columns));
                }
                if (j + 2 < columns && i - 1 >= 0) {
                    graph.addEdge(transform(i, j, columns), transform(j + 2, i - 1, columns));
                }
                if (j - 2 >= 0 && i + 1 < rows) {
                    graph.addEdge(transform(i, j, columns), transform(j - 2, i + 1, columns));
                }
                if (j - 2 >= 0 && i - 1 >= 0) {
                    graph.addEdge(transform(i, j, columns), transform(j - 2, i - 1, columns));
                }
            }
        }

        int from = transform(x1, y1, columns);
        int to = transform(x2, y2, columns);
        //int steps = bfsSearch(graph, from, to);
        int steps = graph.bfs(from, to);
        System.out.println(steps);

    }

    public static int transform(int i, int j, int n) {
        return i * n + j;
    }

    public static int bfsSearch(Graph<Integer> g, int from, int to) {
        Queue<Integer> nodes = new LinkedList<>();
        Queue<Integer> steps = new LinkedList<>();
        HashSet<Integer> visited = new HashSet<>();
        nodes.add(from);
        steps.add(0);
        while (!nodes.isEmpty()) {
            int c = nodes.poll();
            int st = steps.poll();
            if (visited.contains(c)) {
                continue;
            }
            visited.add(c);
            if (c == to) {
                return st;
            }
            GraphNode<Integer> current = g.adjList[c];
            for (GraphNode<Integer> neighbor : current.getNeighbors()) {
                nodes.add(neighbor.getIndex());
                steps.add(st + 1);
            }
        }
        return -1;
    }

    public static <T> void printMatrix(T matrix[][]) {
        System.out.println("Main.");
        Arrays.stream(matrix)
                .map(Arrays::toString)
                .forEach(System.out::println);
    }

    public static boolean isInside(int x, int y, int N) {
        if (x >= 1 && x <= N && y >= 1 && y <= N) return true;
        return false;
    }

    public static int minStepToReachTarget(int knightPos[], int targetPos[], int N) {
        //  x and y direction, where a knight can move
        int dx[] = {-2, -1, 1, 2, -2, -1, 1, 2};
        int dy[] = {-1, -2, -2, -1, 1, 2, 2, 1};

        //  queue for storing states of knight in board
        Queue<Cell> queue = new LinkedList<>();

        //  push starting position of knight with 0 distance
        queue.add(new Cell(knightPos[0], knightPos[1], 0));

        Cell t;
        int x, y;
        boolean visited[][] = new boolean[N + 1][N + 1];

        //  make all cell unvisited
        for (int i = 1; i <= N; i++)
            for (int j = 1; j <= N; j++)
                visited[i][j] = false;

        //  visit starting state
        visited[knightPos[0]][knightPos[1]] = true;

        //  loop until we have one element in queue
        while (!queue.isEmpty()) {
            t = queue.poll();
            visited[t.x][t.y] = true;

            // if current cell is equal to target cell,
            // return its distance
            if (t.x == targetPos[0] && t.y == targetPos[1])
                return t.dis;

            //  loop for all reachable states
            for (int i = 0; i < dx.length; i++) {
                x = t.x + dx[i];
                y = t.y + dy[i];

                // If rechable state is not yet visited and
                // inside board, push that state into queue
                if (isInside(x, y, N) && !visited[x][y])
                    queue.add(new Cell(x, y, t.dis + 1));

            }
        }
        return -1;
    }


}

class GraphNode<E> {
    private int index;//index (reden broj) na temeto vo grafot
    private E info;
    private LinkedList<GraphNode<E>> neighbors;

    public GraphNode(int index, E info) {
        this.index = index;
        this.info = info;
        neighbors = new LinkedList<GraphNode<E>>();
    }

    boolean containsNeighbor(GraphNode<E> o) {
        return neighbors.contains(o);
    }

    void addNeighbor(GraphNode<E> o) {
        neighbors.add(o);
    }


    void removeNeighbor(GraphNode<E> o) {
        if (neighbors.contains(o))
            neighbors.remove(o);
    }


    @Override
    public String toString() {
        String ret = "INFO:" + info + " SOSEDI:";
        for (int i = 0; i < neighbors.size(); i++)
            ret += neighbors.get(i).info + " ";
        return ret;

    }

    @Override
    public boolean equals(Object obj) {
        @SuppressWarnings("unchecked")
        GraphNode<E> pom = (GraphNode<E>) obj;
        return (pom.info.equals(this.info));
    }

    public int getIndex() {
        return index;
    }

    public void setIndex(int index) {
        this.index = index;
    }

    public E getInfo() {
        return info;
    }

    public void setInfo(E info) {
        this.info = info;
    }

    public LinkedList<GraphNode<E>> getNeighbors() {
        return neighbors;
    }

    public void setNeighbors(LinkedList<GraphNode<E>> neighbors) {
        this.neighbors = neighbors;
    }


}

class Graph<E> {

    int num_nodes;
    GraphNode<E> adjList[];

    @SuppressWarnings("unchecked")
    public Graph(int num_nodes, E[] list) {
        this.num_nodes = num_nodes;
        adjList = (GraphNode<E>[]) new GraphNode[num_nodes];
        for (int i = 0; i < num_nodes; i++)
            adjList[i] = new GraphNode<E>(i, list[i]);
    }

    @SuppressWarnings("unchecked")
    public Graph(int num_nodes) {
        this.num_nodes = num_nodes;
        adjList = (GraphNode<E>[]) new GraphNode[num_nodes];
        for (int i = 0; i < num_nodes; i++)
            adjList[i] = new GraphNode<E>(i, null);
    }

    int adjacent(int x, int y) {
        // proveruva dali ima vrska od jazelot so
        // indeks x do jazelot so indeks y
        return (adjList[x].containsNeighbor(adjList[y])) ? 1 : 0;
    }

    void addEdge(int x, int y) {
        // dodava vrska od jazelot so indeks x do jazelot so indeks y
        if (!adjList[x].containsNeighbor(adjList[y])) {
            adjList[x].addNeighbor(adjList[y]);
        }
    }

    void deleteEdge(int x, int y) {
        adjList[x].removeNeighbor(adjList[y]);
    }

    /************************TOPOLOGICAL SORT*******************************************************************/

    void dfsVisit(Stack<Integer> s, int i, boolean[] visited) {
        if (!visited[i]) {
            visited[i] = true;
            Iterator<GraphNode<E>> it = adjList[i].getNeighbors().iterator();
            System.out.println("dfsVisit: " + i + " Stack=" + s);
            while (it.hasNext()) {
                dfsVisit(s, it.next().getIndex(), visited);
            }
            s.push(i);
            System.out.println("--dfsVisit: " + i + " Stack=" + s);
        }
    }

    void topological_sort_dfs() {
        boolean visited[] = new boolean[num_nodes];
        for (int i = 0; i < num_nodes; i++) {
            visited[i] = false;
        }

        Stack<Integer> s = new Stack<Integer>();

        for (int i = 0; i < num_nodes; i++) {
            dfsVisit(s, i, visited);
        }
        System.out.println("----Stack=" + s);
        while (!s.isEmpty()) {
            System.out.println(adjList[s.pop()]);
        }
    }

    /***********************************************************************************************************/


    int bfs(int node, int to) {
        // visited array filled with false
        boolean visited[] = new boolean[num_nodes];
        for (int i = 0; i < num_nodes; i++)
            visited[i] = false;

        // mark start as true
        visited[node] = true;
        // print it
        //System.out.println(node + ": " + adjList[node].getInfo());

        // enqueue the start
        Queue<Integer> queue = new LinkedList<>();
        queue.add(node);

        GraphNode<E> rearmost;

        Queue<Integer> level = new LinkedList<>();
        level.add(0);
        while (!queue.isEmpty()) {
            // dequeue the rear-most
            rearmost = adjList[queue.poll()];
            GraphNode<E> neighbor = null;

            int currentLevel = level.poll();

            // for all of its neighbors
            for (int i = 0; i < rearmost.getNeighbors().size(); i++) {
                neighbor = rearmost.getNeighbors().get(i);

                // find the first neighbor that isn't visited
                if (!visited[neighbor.getIndex()]) {
                    // mark it as visited
                    visited[neighbor.getIndex()] = true;
                    //System.out.println(neighbor.getIndex() + ": " + neighbor.getInfo());
                    // enqueue that neighbor
                    queue.add(neighbor.getIndex());
                    level.add(currentLevel + 1);
                    if (neighbor.getIndex() == to)
                        return currentLevel + 1;
                }
            }

        }
        return -1;
    }


    @Override
    public String toString() {
        String ret = new String();
        for (int i = 0; i < this.num_nodes; i++)
            ret += i + ": " + adjList[i] + "\n";
        return ret;
    }

}

class Cell {
    Integer x;
    Integer y;
    Integer dis;

    public Cell(Integer x, Integer y, Integer dis) {
        this.x = x;
        this.y = y;
        this.dis = dis;
    }
}

/**
 * Дадена е една шаховска табла mxn и на неа е даден една шаховска фигура - коњ поставен во некое поле (x,y) на таблата. Коњот на шаховската табла легално во еден потег може да се движи или за две позиции вертикално и една хоризонтално или за две позиции хоризонтално и една вертикално, т.е. од позиција (x,y) може да се движи на една од следните позиции (x±1,y±2) или (x±2,y±1) (види слика). Да се најде минималниот број на потези за коњот да се придвижи од едно дадено почетно поле до едно дадено крајно поле на таблата.
 * <p>
 * enter image description here
 * <p>
 * Влез: Во првиот ред од влезот се дадени бројот на редици и колони на таблата (5<=m,n<=100), а во вториот ред се дадени полињата на почетокот и крајот на движењето на коњот (x1,y1) и (x2,y2) .
 * <p>
 * Излез: Да се испечати минималниот број на потези за коњот да се придвижи од едно дадено почетно поле до едно дадено крајно поле на таблата.
 * <p>
 * Делумно решение: Задачата се смета за делумно решена доколку се поминати 4 тест примери.
 * <p>
 * Пример:
 * <p>
 * Влез:
 * <p>
 * 5 5
 * <p>
 * 1 2 4 3
 * <p>
 * Излез:
 * <p>
 * 2
 * <p>
 * За да коњот се придвижи од позиција (1,2) до позиција (4,3) на шаховска табла 5x5 потребни се минимум 2 потега.
 * <p>
 * Име на класа (Јава): Board
 */