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Commit 052fc91

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melmedanymelmedany
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cracking conding interview solutions
1 parent f4c37ad commit 052fc91

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‎src/main/java/BinaryTree.java‎

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import java.util.LinkedList;
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import java.util.Queue;
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/**
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* @author medany
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*/
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/*
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* Given the root of a tree node, return the max height of a Binary Tree
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*/
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public class BinaryTree {
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public int solve(TreeNode node) {
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if (node == null)
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return 0;
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Queue<TreeNode> nodes = new LinkedList<>();
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nodes.add(node);
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int height = 0;
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while (true) {
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int c = nodes.size();
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if (c == 0)
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return height;
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height++;
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while (c > 0) {
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TreeNode next = nodes.peek();
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nodes.remove();
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if (next.left != null)
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nodes.add(next.left);
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if (next.right != null)
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nodes.add(next.right);
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c--;
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}
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}
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}
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public int solveRecursive(TreeNode node) {
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if (node == null)
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return 0;
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else {
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/* compute the depth of each subtree */
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int lDepth = solveRecursive(node.left);
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int rDepth = solveRecursive(node.right);
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/* use the larger one */
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if (lDepth > rDepth)
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return (lDepth + 1);
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else
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return (rDepth + 1);
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}
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}
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}

‎src/main/java/BinaryTree2.java‎

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/**
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* @author medany
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*/
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/*
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* Given the root node of a binary tree, can you determine if it's also a binary
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* search tree? Constraints : 0 <= data <= 1000
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*/
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public class BinaryTree2 {
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boolean solve(TreeNode root) {
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return solve(root, -1, 10001);
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}
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private boolean solve(TreeNode root, int min, int max) {
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if (root == null)
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return true;
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if (root.data <= min || root.data >= max)
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return false;
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return (solve(root.left, min, root.data) && solve(root.right, root.data, max));
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}
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}

‎src/main/java/Contacts.java‎

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import java.util.ArrayList;
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import java.util.HashMap;
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import java.util.List;
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import java.util.Map;
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import java.util.TreeMap;
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/**
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* @author medany
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*/
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public class Contacts {
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public Integer[] solve(String[] lines, int f) {
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ContactsManager contacts = new ContactsManager();
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String operation, contact, pattern;
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Integer[] result = new Integer[f];
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int r = 0;
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for (String line : lines) {
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operation = line.split(" ")[0];
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if (operation.equals("add")) {
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contact = line.split(" ")[1];
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contacts.add(contact);
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} else if (operation.equals("find")) {
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pattern = line.split(" ")[1];
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result[r] = contacts.find(pattern);
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r++;
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}
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}
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return result;
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}
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}
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class ContactsManager {
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private Map<Character, Map<Character, List<String>>> book;
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public ContactsManager() {
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this.book = new TreeMap<>();
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}
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public void add(String name) {
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if (book.containsKey(name.charAt(0))) {
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if (book.get(name.charAt(0)).containsKey(name.charAt(1))) {
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book.get(name.charAt(0)).get(name.charAt(1)).add(name);
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} else {
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book.get(name.charAt(0)).put(name.charAt(1), new ArrayList<String>());
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book.get(name.charAt(0)).get(name.charAt(1)).add(name);
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}
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} else {
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book.put(name.charAt(0), new HashMap<Character, List<String>>());
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if (name.length() > 1) {
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book.get(name.charAt(0)).put(name.charAt(1), new ArrayList<String>());
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book.get(name.charAt(0)).get(name.charAt(1)).add(name);
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} else {
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book.get(name.charAt(0)).put(name.charAt(0), new ArrayList<String>());
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book.get(name.charAt(0)).get(name.charAt(0)).add(name);
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}
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}
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}
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public int find(String pattern) {
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int count = 0;
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if (pattern.length() < 2) {
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if (book.containsKey(pattern.charAt(0))) {
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for (List<String> list : book.get(pattern.charAt(0)).values())
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count += list.size();
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}
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} else {
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if (book.containsKey(pattern.charAt(0))) {
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if (book.get(pattern.charAt(0)).containsKey(pattern.charAt(1)))
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for (String contact : book.get(pattern.charAt(0)).get(pattern.charAt(1))) {
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if (contact.startsWith(pattern)) {
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count++;
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}
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}
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}
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}
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return count;
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}
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}

‎src/main/java/TreeNode.java‎

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/**
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* @author medany
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*/
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public class TreeNode {
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int data;
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TreeNode left, right;
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TreeNode(int data) {
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this.data = data;
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left = right = null;
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}
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@Override
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public String toString() {
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return data + ", ";
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}
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}

‎test/main/java/BinaryTree2Test.java‎

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import org.junit.Assert;
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import org.junit.Test;
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/**
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* @author medany
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*/
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public class BinaryTree2Test {
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private BinaryTree2 alg = new BinaryTree2();
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private boolean actual, expected;
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@Test
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public void Test_Recursive_1() {
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TreeNode root = new TreeNode(4);
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root.left = new TreeNode(2);
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root.right = new TreeNode(6);
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root.left.left = new TreeNode(1);
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root.left.right = new TreeNode(3);
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root.right.left = new TreeNode(5);
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root.right.right = new TreeNode(7);
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actual = alg.solve(root);
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expected = true;
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Assert.assertEquals(expected, actual);
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}
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@Test
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public void Test_Recursive_2() { // 1 2 4 3 5 6 7
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TreeNode root = new TreeNode(3);
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root.left = new TreeNode(2);
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root.right = new TreeNode(6);
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root.left.left = new TreeNode(1);
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root.left.right = new TreeNode(4);
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root.right.left = new TreeNode(5);
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root.right.right = new TreeNode(7);
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actual = alg.solve(root);
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expected = false;
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Assert.assertEquals(expected, actual);
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}
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}

‎test/main/java/BinaryTreeTest.java‎

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import org.junit.Assert;
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import org.junit.Test;
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/**
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* @author medany
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*/
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public class BinaryTreeTest {
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private BinaryTree alg = new BinaryTree();
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private int actual, expected;
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@Test
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public void Test_Iterative() {
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TreeNode root = new TreeNode(1);
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root.left = new TreeNode(2);
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root.right = new TreeNode(3);
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root.left.left = new TreeNode(4);
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root.left.right = new TreeNode(5);
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actual = alg.solve(root);
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expected = 3;
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Assert.assertEquals(expected, actual);
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}
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@Test
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public void Test_Recursive() {
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TreeNode root = new TreeNode(1);
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root.left = new TreeNode(2);
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root.right = new TreeNode(3);
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root.left.left = new TreeNode(4);
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root.left.right = new TreeNode(5);
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actual = alg.solve(root);
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expected = 3;
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Assert.assertEquals(expected, actual);
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}
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}

‎test/main/java/ContactsTest.java‎

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import java.io.BufferedReader;
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import java.io.File;
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import java.io.FileReader;
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import java.io.IOException;
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import org.junit.Assert;
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import org.junit.Test;
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/**
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* @author medany
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*/
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public class ContactsTest {
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private Contacts alg = new Contacts();
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Integer[] actual = null, expected = null;
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@Test
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public void Test_1() {
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actual = alg.solve(new String[] { "add hack", "add hackerrank", "find hac", "find hak" }, 2);
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expected = new Integer[] { 2, 0 };
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Assert.assertArrayEquals(expected, actual);
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}
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@Test
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public void Test_2() {
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BufferedReader ir = null, or = null;
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FileReader i = null, o = null;
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try {
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i = new FileReader(new File(this.getClass().getClassLoader().getResource("contacts_input").getPath()));
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o = new FileReader(new File(this.getClass().getClassLoader().getResource("contacts_output").getPath()));
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ir = new BufferedReader(i);
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or = new BufferedReader(o);
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int n = 0;
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String[] lines;
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String line = ir.readLine();
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n = Integer.parseInt(line);
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lines = new String[n];
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int l = 0, f = 0;
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while ((line = ir.readLine()) != null) {
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lines[l] = line;
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if (line.split(" ")[0].equals("find"))
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f++;
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l++;
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}
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expected = new Integer[f];
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l = 0;
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while ((line = or.readLine()) != null) {
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expected[l] = Integer.parseInt(line);
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l++;
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}
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actual = alg.solve(lines, f);
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Assert.assertArrayEquals(expected, actual);
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} catch (IOException e) {
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e.printStackTrace();
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} finally {
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try {
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if (ir != null)
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ir.close();
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if (or != null)
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or.close();
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if (i != null)
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i.close();
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if (o != null)
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o.close();
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} catch (IOException ex) {
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ex.printStackTrace();
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}
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}
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}
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@Test
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public void Test_3() {
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actual = alg.solve(new String[] { "add s", "add ss", "add sss", "add ssss", "add sssss", "find s", "find ss",
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"find sss", "find ssss", "find sssss", "find ssssss" }, 6);
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expected = new Integer[] { 5, 4, 3, 2, 1, 0 };
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Assert.assertArrayEquals(expected, actual);
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}
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}

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