implement the insertion in binary search tree and print its preorder.

 class Node {

  constructor(value) {

    this.value = value;

    this.left = null;

    this.right = null;

  }

}

 

// Define the BinarySearchTree class

class BinarySearchTree {

  constructor() {

    this.root = null;

  }

 

  // Insert a new node with the given value

  insert(value) {

    const newNode = new Node(value);

    if (!this.root) {

      this.root = newNode;

      return this;

    }

    let current = this.root;

    while (true) {

      if (value === current.value) {

        return undefined;

      }

      if (value < current.value) {

        if (current.left === null) {

          current.left = newNode;

          return this;

        }

        current = current.left;

      } else {

        if (current.right === null) {

          current.right = newNode;

          return this;

        }

        current = current.right;

      }

    }

  }

 

  // Print the preorder traversal of the tree

  preorder() {

    let result = [];

    function traverse(node) {

      result.push(node.value);

      if (node.left) traverse(node.left);

      if (node.right) traverse(node.right);

    }

    traverse(this.root);

    return result;

  }

}

 

// Example usage:

const bst = new BinarySearchTree();

bst.insert(10);

bst.insert(5);

bst.insert(15);

bst.insert(3);

bst.insert(7);

bst.insert(12);

bst.insert(18);

console.log(bst.preorder());

 

Output:-

[10, 5, 3, 7, 15, 12, 18]