In this HackerRank Java Visitor Pattern problem in the java programming language, you need to Implement three different visitors and read and build the tree.

HackerRank Java Visitor Pattern problem solution


HackerRank Java Visitor Pattern problem solution.

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

import java.util.ArrayList;
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<Tree> 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<Integer, Tree> tree = new HashMap<>();

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

        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<Integer, ArrayList<Integer>> edges = new HashMap<Integer, ArrayList<Integer>>();

        for (int i = 1; i <= n; i++)
            edges.put(i, new ArrayList<Integer>());

        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.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);
  }
}