// Create a BinaryTree with entries
    const entries: [number, string][] = [
      [6, 'six'],
      [1, 'one'],
      [2, 'two'],
      [7, 'seven'],
      [5, 'five'],
      [3, 'three'],
      [4, 'four'],
      [9, 'nine'],
      [8, 'eight']
    ];

    const tree = new BinaryTree(entries);

    // Verify size
    console.log(tree.size); // 9;

    // Add new element
    tree.add(10, 'ten');
    console.log(tree.size); // 10;

 const tree = new BinaryTree(
      [
        [5, 'five'],
        [3, 'three'],
        [7, 'seven'],
        [1, 'one'],
        [4, 'four'],
        [6, 'six'],
        [8, 'eight']
      ],
      { isMapMode: false }
    );

    // Check if key exists
    console.log(tree.has(5)); // true;
    console.log(tree.has(10)); // false;

    // Get value by key
    console.log(tree.get(3)); // 'three';
    console.log(tree.get(7)); // 'seven';
    console.log(tree.get(100)); // undefined;

    // Get node structure
    const node = tree.getNode(5);
    console.log(node?.key); // 5;
    console.log(node?.value); // 'five';

 const tree = new BinaryTree([
      [1, 'one'],
      [2, 'two'],
      [3, 'three'],
      [4, 'four'],
      [5, 'five'],
      [6, 'six'],
      [7, 'seven']
    ]);

    // Binary tree maintains level-order insertion
    // Complete binary tree structure
    console.log(tree.size); // 7;

    // Verify all keys are present
    console.log(tree.has(1)); // true;
    console.log(tree.has(4)); // true;
    console.log(tree.has(7)); // true;

    // Iterate through tree
    const keys: number[] = [];
    for (const [key] of tree) {
      keys.push(key);
    }
    console.log(keys.length); // 7;

 // Decision tree structure
    const loanDecisionTree = new BinaryTree<string>(
      ['stableIncome', 'goodCredit', 'Rejected', 'Approved', 'Rejected'],
      { isDuplicate: true }
    );

    function determineLoanApproval(
      node?: BinaryTreeNode<string> | null,
      conditions?: { [key: string]: boolean }
    ): string {
      if (!node) throw new Error('Invalid node');

      // If it's a leaf node, return the decision result
      if (!node.left && !node.right) return node.key;

      // Check if a valid condition exists for the current node's key
      return conditions?.[node.key]
        ? determineLoanApproval(node.left, conditions)
        : determineLoanApproval(node.right, conditions);
    }

    // Test case 1: Stable income and good credit score
    console.log(determineLoanApproval(loanDecisionTree.root, { stableIncome: true, goodCredit: true })); // 'Approved';

    // Test case 2: Stable income but poor credit score
    console.log(determineLoanApproval(loanDecisionTree.root, { stableIncome: true, goodCredit: false })); // 'Rejected';

    // Test case 3: No stable income
    console.log(determineLoanApproval(loanDecisionTree.root, { stableIncome: false, goodCredit: true })); // 'Rejected';

    // Test case 4: No stable income and poor credit score
    console.log(determineLoanApproval(loanDecisionTree.root, { stableIncome: false, goodCredit: false })); // 'Rejected';

 const expressionTree = new BinaryTree<number | string>(['+', 3, '*', null, null, 5, '-', null, null, 2, 8]);

    function evaluate(node?: BinaryTreeNode<number | string> | null): number {
      if (!node) return 0;

      if (typeof node.key === 'number') return node.key;

      const leftValue = evaluate(node.left); // Evaluate the left subtree
      const rightValue = evaluate(node.right); // Evaluate the right subtree

      // Perform the operation based on the current node's operator
      switch (node.key) {
        case '+':
          return leftValue + rightValue;
        case '-':
          return leftValue - rightValue;
        case '*':
          return leftValue * rightValue;
        case '/':
          return rightValue !== 0 ? leftValue / rightValue : 0; // Handle division by zero
        default:
          throw new Error(`Unsupported operator: ${node.key}`);
      }
    }

    console.log(evaluate(expressionTree.root)); // -27;