Trees - 1

Author: kunal-kushwaha

lectures/20-trees/code/introduction/BST.java

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+class BST {
+  public class Node {
+    private int value;
+    private Node left;
+    private Node right;
+    private int height;
+
+    public Node(int value) {
+      this.value = value;
+    }
+
+    public int getValue() {
+      return value;
+    }
+  }
+
+  private Node root;
+
+  public BST() {
+
+  }
+
+  public int height(Node node) {
+    if (node == null) {
+      return -1;
+    }
+    return node.height;
+  }
+
+  public boolean isEmpty() {
+    return root == null;
+  }
+
+  public void insert(int value) {
+    root = insert(value, root);
+  }
+
+  private Node insert(int value, Node node) {
+    if (node == null) {
+      node = new Node(value);
+      return node;
+    }
+
+    if (value < node.value) {
+      node.left = insert(value, node.left);
+    }
+
+    if (value > node.value) {
+      node.right = insert(value, node.right);
+    }
+
+    node.height = Math.max(height(node.left), height(node.right)) + 1;
+    return node;
+  }
+
+  public void populate(int[] nums) {
+    for (int i = 0; i < nums.length; i++) {
+      this.insert(nums[i]);
+    }
+  }
+
+  public void populatedSorted(int[] nums) {
+    populatedSorted(nums, 0, nums.length);
+  }
+
+  private void populatedSorted(int[] nums, int start, int end) {
+    if (start >= end) {
+      return;
+    }
+
+    int mid = (start + end) / 2;
+
+    this.insert(nums[mid]);
+    populatedSorted(nums, start, mid);
+    populatedSorted(nums, mid + 1, end);
+  }
+
+  public boolean balanced() {
+    return balanced(root);
+  }
+
+  private boolean balanced(Node node) {
+    if (node == null) {
+      return true;
+    }
+    return Math.abs(height(node.left) - height(node.right)) <= 1 && balanced(node.left) && balanced(node.right);
+  }
+
+  public void display() {
+    display(this.root, "Root Node: ");
+  }
+
+  private void display(Node node, String details) {
+    if (node == null) {
+      return;
+    }
+    System.out.println(details + node.value);
+    display(node.left, "Left child of " + node.value + " : ");
+    display(node.right, "Right child of " + node.value + " : ");
+  }
+
+}

lectures/20-trees/code/introduction/BinaryTree.java

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+import java.util.Scanner;
+
+class BinaryTree {
+
+  public BinaryTree() {
+
+  }
+
+  private static class Node {
+    int value;
+    Node left;
+    Node right;
+
+    public Node(int value) {
+      this.value = value;
+    }
+  }
+
+  private Node root;
+
+  // insert elements
+  public void populate(Scanner scanner) {
+    System.out.println("Enter the root Node: ");
+    int value = scanner.nextInt();
+    root = new Node(value);
+    populate(scanner, root);
+  }
+
+  private void populate(Scanner scanner, Node node) {
+    System.out.println("Do you want to enter left of " + node.value);
+    boolean left = scanner.nextBoolean();
+    if (left) {
+      System.out.println("Enter the value of the left of " + node.value);
+      int value = scanner.nextInt();
+      node.left = new Node(value);
+      populate(scanner, node.left);
+    }
+
+    System.out.println("Do you want to enter right of " + node.value);
+    boolean right = scanner.nextBoolean();
+    if (right) {
+      System.out.println("Enter the value of the right of " + node.value);
+      int value = scanner.nextInt();
+      node.right = new Node(value);
+      populate(scanner, node.right);
+    }
+
+  }
+
+  public void display() {
+    display(this.root, "");
+  }
+
+  private void display(Node node, String indent) {
+    if (node == null) {
+      return;
+    }
+    System.out.println(indent + node.value);
+    display(node.left, indent + "\t");
+    display(node.right, indent + "\t");
+  }
+
+  public void prettyDisplay() {
+    prettyDisplay(root, 0);
+  }
+
+  private void prettyDisplay(Node node, int level) {
+    if (node == null) {
+      return;
+    }
+
+    prettyDisplay(node.right, level + 1);
+
+    if (level != 0) {
+      for (int i = 0; i < level - 1; i++) {
+        System.out.print("|\t\t");
+      }
+      System.out.println("|------->" + node.value);
+    } else {
+      System.out.println(node.value);
+    }
+    prettyDisplay(node.left, level + 1);
+  }
+
+  public void preOrder() {
+    preOrder(root);
+  }
+
+  private void preOrder(Node node) {
+    if (node == null) {
+      return;
+    }
+    System.out.print(node.value + " ");
+    preOrder(node.left);
+    preOrder(node.right);
+  }
+
+  public void inOrder() {
+    preOrder(root);
+  }
+
+  private void inOrder(Node node) {
+    if (node == null) {
+      return;
+    }
+    preOrder(node.left);
+    System.out.print(node.value + " ");
+    preOrder(node.right);
+  }
+
+  public void postOrder() {
+    preOrder(root);
+  }
+
+  private void postOrder(Node node) {
+    if (node == null) {
+      return;
+    }
+    preOrder(node.left);
+    preOrder(node.right);
+    System.out.print(node.value + " ");
+  }
+
+}

lectures/20-trees/code/introduction/Main.java

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+import java.util.Scanner;
+
+public class Main {
+  public static void main(String[] args) {
+    // Scanner scanner = new Scanner(System.in);
+    // BinaryTree tree = new BinaryTree();
+    // tree.populate(scanner);
+    // tree.prettyDisplay();
+
+    BST tree = new BST();
+    int[] nums = { 5, 2, 7, 1, 4, 6, 9, 8, 3, 10 };
+    tree.populate(nums);
+    tree.display();
+  }
+}