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Java Visitor Pattern

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  • pw_hackerrank
     + 0 comments

    The problem description is tricky and easily misleading. Specifically it says:

    ...Each of the subsequent lines contains two space-separated integers, *ui* and *vi* , describing an edge between nodes *u* and *v*.

    An edge input like this:

    3 4

    does not mean that 3 is the parent. The parent may as well be noted on the right side. The correct interpretation:

    There is just a link between 3 and 4, it's unspecified which one is tree node/leaf node.

  • paburnwal123
     + 0 comments

    Can anyone tell me what do we have to do in this module

  • nashruddinshaik
     + 0 comments

    This code works fine for me

    import java.util.ArrayList; import java.util.HashMap; import java.util.Map; import java.util.Scanner; import java.util.Iterator;

    enum Color { RED, GREEN }

    abstract class Tree { private int value; private Color color; private int depth;

    public Tree(int value, Color color, int depth) {
    this.value = value;
    this.color = color;
    this.depth = depth;
}

public int getValue() {
    return value;
}

public Color getColor() {
    return color;
}

public int getDepth() {
    return depth;
}

public abstract void accept(TreeVis visitor);

    }

    class TreeNode extends Tree { private ArrayList children = new ArrayList<>();

    public TreeNode(int value, Color color, int depth) {
    super(value, color, depth);
}

public void accept(TreeVis visitor) {
    visitor.visitNode(this);
    for (Tree child : children) {
        child.accept(visitor);
    }
}

public void addChild(Tree child) {
    children.add(child);
}

    }

    class TreeLeaf extends Tree { public TreeLeaf(int value, Color color, int depth) { super(value, color, depth); }

    public void accept(TreeVis visitor) {
    visitor.visitLeaf(this);
}

    }

    abstract class TreeVis { public abstract int getResult(); public abstract void visitNode(TreeNode node); public abstract void visitLeaf(TreeLeaf leaf); }

    class SumInLeavesVisitor extends TreeVis { private int sumInLeaves = 0;

    public int getResult() {
    return sumInLeaves;
}

public void visitNode(TreeNode node) {
    // Do nothing for nodes
}

public void visitLeaf(TreeLeaf leaf) {
    sumInLeaves += leaf.getValue();
}

    }

    class ProductOfRedNodesVisitor extends TreeVis { private long productOfRedNodes = 1L; private static final int MOD = 1000000007;

    public int getResult() {
    return (int) productOfRedNodes;
}

private void multiply(Tree tree) {
    if (tree.getColor() == Color.RED) {
        productOfRedNodes = (productOfRedNodes * tree.getValue()) % MOD;
    }
}

public void visitNode(TreeNode node) {
    multiply(node);
}

public void visitLeaf(TreeLeaf leaf) {
    multiply(leaf);
}

    }

    class FancyVisitor extends TreeVis { private int sumOfValuesNonLeafEvenDepth = 0; private int sumOfValuesGreenLeaf = 0;

    public int getResult() {
    return Math.abs(sumOfValuesNonLeafEvenDepth - sumOfValuesGreenLeaf);
}

public void visitNode(TreeNode node) {
    if (node.getDepth() % 2 == 0) {
        sumOfValuesNonLeafEvenDepth += node.getValue();
    }
}

public void visitLeaf(TreeLeaf leaf) {
    if (leaf.getColor() == Color.GREEN) {
        sumOfValuesGreenLeaf += leaf.getValue();
    }
}

    }

    public class Solution { static Map tree = new HashMap<>();

    public static Tree solve() {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    Map<Integer, Object[]> nodeAtts = new HashMap<>();

    // Read node values
    for (int i = 0; i < n; i++) {
        nodeAtts.put(i + 1, new Object[]{sc.nextInt(), null});
    }

    // Read node colors
    for (int i = 0; i < n; i++) {
        nodeAtts.get(i + 1)[1] = sc.nextInt() == 0 ? Color.RED : Color.GREEN;
    }

    // Read edges
    Map<Integer, ArrayList<Integer>> edges = new HashMap<>();
    for (int i = 1; i <= n; i++) {
        edges.put(i, new ArrayList<>());
    }

    for (int i = 1; i < n; i++) {
        int u = sc.nextInt();
        int v = sc.nextInt();
        edges.get(u).add(v);
        edges.get(v).add(u);
    }

    // Create root node
    Tree root = new TreeNode((Integer) nodeAtts.get(1)[0], (Color) nodeAtts.get(1)[1], 0);
    tree.put(1, root);

    // Perform DFS to build tree
    DFS(n, edges, nodeAtts);
    return tree.get(1);
}

private static void DFS(int n, Map<Integer, ArrayList<Integer>> edges, Map<Integer, Object[]> nodeAtts) {
    boolean[] visited = new boolean[n + 1];
    TreeNode parent = (TreeNode) tree.get(1);
    DFSUtil(parent, 1, visited, edges, nodeAtts);
}

private static void DFSUtil(TreeNode parent, int v, boolean[] visited, Map<Integer, ArrayList<Integer>> edges, Map<Integer, Object[]> nodeAtts) {
    visited[v] = true;

    if (v != 1 && edges.get(v).size() == 1) {
        TreeLeaf treeLeaf = new TreeLeaf((Integer) nodeAtts.get(v)[0], (Color) nodeAtts.get(v)[1], parent.getDepth() + 1);
        parent.addChild(treeLeaf);
        tree.put(v, treeLeaf);
        return;
    }

    TreeNode treeNode = (v != 1) ? new TreeNode((Integer) nodeAtts.get(v)[0], (Color) nodeAtts.get(v)[1], parent.getDepth() + 1) : (TreeNode) tree.get(1);

    if (v != 1) {
        parent.addChild(treeNode);
        tree.put(v, treeNode);
    }

    for (int n : edges.get(v)) {
        if (!visited[n]) {
            DFSUtil(treeNode, n, visited, edges, nodeAtts);
        }
    }
}

public static void main(String[] args) {
    Tree root = solve();
    SumInLeavesVisitor vis1 = new SumInLeavesVisitor();
    ProductOfRedNodesVisitor vis2 = new ProductOfRedNodesVisitor();
    FancyVisitor vis3 = new FancyVisitor();

    root.accept(vis1);
    root.accept(vis2);
    root.accept(vis3);

    System.out.println(vis1.getResult());
    System.out.println(vis2.getResult());
    System.out.println(vis3.getResult());
}

    }

  • shashankk9650
     + 0 comments

    import java.util.ArrayList; import java.util.HashMap; import java.util.Iterator; import java.util.Map; import java.util.Scanner;

    enum Color { RED, GREEN } abstract class Tree { private int value; private Color color; private int depth; public Tree( int value, Color color, int depth ) { this.value = value; this.color = color; this.depth = depth; }

    public int getValue()
{
    return value;
}

public Color getColor()
{
    return color;
}

public int getDepth()
{
    return depth;
}

public abstract void accept( TreeVis visitor );

    } class TreeNode extends Tree { private ArrayList children = new ArrayList<>(); public TreeNode( int value, Color color, int depth ) { super( value, color, depth ); }

    public void accept( TreeVis visitor )
{
    visitor.visitNode( this );
    for ( Tree child : children )
    {
        child.accept( visitor );
    }
}

public void addChild( Tree child )
{
    children.add( child );
}

    } class TreeLeaf extends Tree { public TreeLeaf( int value, Color color, int depth ) { super( value, color, depth ); }

    public void accept( TreeVis visitor )
{
    visitor.visitLeaf( this );
}

    } abstract class TreeVis { public abstract int getResult();

    public abstract void visitNode( TreeNode node );

public abstract void visitLeaf( TreeLeaf leaf );

    } class SumInLeavesVisitor extends TreeVis { int sumInLeaves = 0; public int getResult() { return sumInLeaves; }

    public void visitNode( TreeNode node )
{
    // empty return
}

public void visitLeaf( TreeLeaf leaf )
{
    sumInLeaves += leaf.getValue();
}

    } class ProductOfRedNodesVisitor extends TreeVis { long productOfRedNodes = 1L; public int getResult() { return (int) ( productOfRedNodes ); }

    void multiply( Tree tree )
{
    if ( tree.getColor() == Color.RED )
    {
        productOfRedNodes = ( productOfRedNodes * tree.getValue() ) % ( 1000000007 );
    }
}

public void visitNode( TreeNode node )
{
    multiply( node );
}

public void visitLeaf( TreeLeaf leaf )
{
    multiply( leaf );
}

    } class FancyVisitor extends TreeVis { int sumOfValuesNonLeafEvenDepth = 0; int sumOfValuesGreenLeaf = 0; public int getResult() { return Math.abs( sumOfValuesGreenLeaf - sumOfValuesNonLeafEvenDepth ); }

    public void visitNode( TreeNode node )
{
    if ( node.getDepth() % 2 != 0 )
        return;
    sumOfValuesNonLeafEvenDepth += node.getValue();
}

public void visitLeaf( TreeLeaf leaf )
{
    if ( leaf.getColor() != Color.GREEN )
        return;
    sumOfValuesGreenLeaf += leaf.getValue();
}

    } public class Solution { static Map tree = new HashMap<>(); public static Tree solve() { Scanner sc = new Scanner( System.in ); int n = sc.nextInt(); Map nodeAtts = new HashMap<>(); for ( int i = 0; i < n; i++ ) { nodeAtts.put( i + 1, new Object[] { sc.nextInt(), null } ); } for ( int i = 0; i < n; i++ ) { nodeAtts.get( i + 1 )[1] = sc.nextInt() == 0 ? Color.RED : Color.GREEN; } Map> edges = new HashMap<>(); for ( int i = 1; i <= n; i++ ) { edges.put( i, new ArrayList<>() ); } for ( int i = 1; i < n; i++ ) { int u = sc.nextInt(); int v = sc.nextInt(); edges.get( u ).add( v ); edges.get( v ).add( u ); } Tree root = new TreeNode( (Integer) nodeAtts.get( 1 )[0], (Color) nodeAtts.get( 1 )[1], 0 ); tree.put( 1, root ); DFS( n, edges, nodeAtts ); return (Tree) tree.get( 1 ); }

    private static void DFS( int n, Map<Integer, ArrayList<Integer>> edges, Map<Integer, Object[]> nodeAtts )
{
    boolean[] visited = new boolean[n + 1];
    TreeNode parent = (TreeNode) tree.get( 1 );
    DFSUtil( parent, 1, visited, edges, nodeAtts );
}

private static void DFSUtil( TreeNode parent,
                             int v,
                             boolean[] visited,
                             Map<Integer, ArrayList<Integer>> edges,
                             Map<Integer, Object[]> nodeAtts )
{
    visited[v] = true;
    if ( edges.get( v ).size() == 1 && v != 1 )
    {
        TreeLeaf treeLeaf = new TreeLeaf( (Integer) nodeAtts.get( v )[0],
                                          (Color) nodeAtts.get( v )[1],
                                          parent.getDepth() + 1 );
        parent.addChild( treeLeaf );
        tree.put( v, treeLeaf );
        return;
    }
    TreeNode treeNode;
    if ( v != 1 )
    {
        treeNode = new TreeNode( (Integer) nodeAtts.get( v )[0],
                                 (Color) nodeAtts.get( v )[1],
                                 parent.getDepth() + 1 );
        parent.addChild( treeNode );
        tree.put( v, treeNode );
    }
    else
    {
        treeNode = (TreeNode) tree.get( 1 );
    }
    Iterator<Integer> iterator = edges.get( v ).iterator();
    while ( iterator.hasNext() )
    {
        int n = iterator.next();
        if ( !visited[n] )
        {
            DFSUtil( treeNode, n, visited, edges, nodeAtts );
        }
    }
}

public static void main( String[] args )
{
    Tree root = solve();
    SumInLeavesVisitor vis1 = new SumInLeavesVisitor();
    ProductOfRedNodesVisitor vis2 = new ProductOfRedNodesVisitor();
    FancyVisitor vis3 = new FancyVisitor();
    root.accept( vis1 );
    root.accept( vis2 );
    root.accept( vis3 );
    int res1 = vis1.getResult();
    int res2 = vis2.getResult();
    int res3 = vis3.getResult();
    System.out.println( res1 );
    System.out.println( res2 );
    System.out.println( res3 );
}

    }

  • madhuganesh35
     + 0 comments

    this code is working in JDK 8

    import java.util.ArrayList; import java.io.; import java.util.; import java.text.; import java.math.; import java.util.regex.*;

    enum Color { RED, GREEN }

    abstract class Tree { private int value; private Color color; private int depth;

    public Tree(int value, Color color, int depth) { this.value = value; this.color = color; this.depth = depth; }

    public int getValue() { return value; }

    public Color getColor() { return color; }

    public int getDepth() { return depth; }

    public abstract void accept(TreeVis visitor); }

    class TreeNode extends Tree { private ArrayList children = new ArrayList<>();

    public TreeNode(int value, Color color, int depth) { super(value, color, depth); }

    public void accept(TreeVis visitor) { visitor.visitNode(this); for (Tree child : children) { child.accept(visitor); } }

    public void addChild(Tree child) { children.add(child); } }

    class TreeLeaf extends Tree { public TreeLeaf(int value, Color color, int depth) { super(value, color, depth); }

    public void accept(TreeVis visitor) { visitor.visitLeaf(this); } }

    abstract class TreeVis { public abstract int getResult();

    public abstract void visitNode(TreeNode node);

    public abstract void visitLeaf(TreeLeaf leaf); }

    class SumInLeavesVisitor extends TreeVis { int sumInLeaves = 0;

    public int getResult() { return sumInLeaves; }

    public void visitNode(TreeNode node) { // empty return }

    public void visitLeaf(TreeLeaf leaf) { sumInLeaves += leaf.getValue(); } }

    class ProductOfRedNodesVisitor extends TreeVis { long productOfRedNodes = 1L;

    public int getResult() { return (int) (productOfRedNodes); }

    void multiply(Tree tree) { if (tree.getColor() == Color.RED) { productOfRedNodes = (productOfRedNodes * tree.getValue()) % (1000000007); } }

    public void visitNode(TreeNode node) { multiply(node); }

    public void visitLeaf(TreeLeaf leaf) { multiply(leaf); } }

    class FancyVisitor extends TreeVis { int sumOfValuesNonLeafEvenDepth = 0; int sumOfValuesGreenLeaf = 0;

    public int getResult() { return Math.abs(sumOfValuesGreenLeaf - sumOfValuesNonLeafEvenDepth); }

    public void visitNode(TreeNode node) { if (node.getDepth() % 2 != 0) return; sumOfValuesNonLeafEvenDepth += node.getValue(); }

    public void visitLeaf(TreeLeaf leaf) { if (leaf.getColor() != Color.GREEN) return; sumOfValuesGreenLeaf += leaf.getValue(); } }

    public class Solution { static Map tree = new HashMap<>();

    public static Tree solve() { Scanner sc = new Scanner(System.in); int n = sc.nextInt(); Map nodeAtts = new HashMap<>(); for (int i = 0; i < n; i++) { nodeAtts.put(i + 1, new Object[]{sc.nextInt(), null}); } for (int i = 0; i < n; i++) { nodeAtts.get(i + 1)[1] = sc.nextInt() == 0 ? Color.RED : Color.GREEN; } Map> edges = new HashMap<>(); for (int i = 1; i <= n; i++) { edges.put(i, new ArrayList<>()); } for (int i = 1; i < n; i++) { int u = sc.nextInt(); int v = sc.nextInt(); edges.get(u).add(v); edges.get(v).add(u); } Tree root = new TreeNode((Integer) nodeAtts.get(1)[0], (Color) nodeAtts.get(1)[1], 0); tree.put(1, root); DFS(n, edges, nodeAtts); return (Tree) tree.get(1); }

    private static void DFS(int n, Map> edges, Map nodeAtts) { boolean[] visited = new boolean[n + 1]; TreeNode parent = (TreeNode) tree.get(1); DFSUtil(parent, 1, visited, edges, nodeAtts); }

    private static void DFSUtil(TreeNode parent, int v, boolean[] visited, Map> edges, Map nodeAtts) { visited[v] = true; if (edges.get(v).size() == 1 && v != 1) { TreeLeaf treeLeaf = new TreeLeaf((Integer) nodeAtts.get(v)[0], (Color) nodeAtts.get(v)[1], parent.getDepth() + 1); parent.addChild(treeLeaf); tree.put(v, treeLeaf); return; } TreeNode treeNode; if (v != 1) { treeNode = new TreeNode((Integer) nodeAtts.get(v)[0], (Color) nodeAtts.get(v)[1], parent.getDepth() + 1); parent.addChild(treeNode); tree.put(v, treeNode); } else { treeNode = (TreeNode) tree.get(1); } Iterator iterator = edges.get(v).iterator(); while (iterator.hasNext()) { int n = iterator.next(); if (!visited[n]) { DFSUtil(treeNode, n, visited, edges, nodeAtts); } } }

    public static void main(String[] args) { Tree root = solve(); SumInLeavesVisitor vis1 = new SumInLeavesVisitor(); ProductOfRedNodesVisitor vis2 = new ProductOfRedNodesVisitor(); FancyVisitor vis3 = new FancyVisitor(); root.accept(vis1); root.accept(vis2); root.accept(vis3); int res1 = vis1.getResult(); int res2 = vis2.getResult(); int res3 = vis3.getResult(); System.out.println(res1); System.out.println(res2); System.out.println(res3); } }