Tree Traversal Preorder Root Left Right in DSA Typescript - Build from Scratch

Tree Traversal Preorder Root Left Right

📖 Scenario: You are working with a simple family tree where each person can have up to two children. You want to visit each person starting from the oldest ancestor, then their left child, then their right child.

🎯 Goal: Build a program that creates a tree structure and prints the names of people in preorder traversal order: root first, then left child, then right child.

📋 What You'll Learn

Create a tree node class with name, left, and right properties

Create a tree with exactly three nodes: "Grandparent", "Parent", and "Child"

Write a preorder traversal function called preorderTraversal that visits nodes in root-left-right order

Print the names of the nodes in preorder traversal separated by spaces

💡 Why This Matters

🌍 Real World

Tree traversal is used in many real-world applications like file system navigation, organization charts, and parsing expressions.

💼 Career

Understanding tree traversal is essential for software developers working with hierarchical data, databases, and algorithms.

1

Create TreeNode class and build the tree

Create a class called TreeNode with a constructor that takes a name string and sets left and right to null. Then create three nodes: grandparent with name "Grandparent", parent with name "Parent", and child with name "Child". Connect grandparent.left to parent and parent.left to child.

DSA Typescript

// Your code here

Hint

Define the TreeNode class with name, left, and right. Then create the three nodes and link them as described.

2

Create a helper array to store traversal result

Create an empty array called result of type string[] to store the names of nodes during traversal.

DSA Typescript

class TreeNode {
    name: string;
    left: TreeNode | null;
    right: TreeNode | null;

    constructor(name: string) {
        this.name = name;
        this.left = null;
        this.right = null;
    }
}

const grandparent = new TreeNode("Grandparent");
const parent = new TreeNode("Parent");
const child = new TreeNode("Child");

grandparent.left = parent;
parent.left = child;

// Create an empty array called result to store traversal names
// Your code here

Hint

Just create an empty array named result to hold the names as strings.

3

Write preorder traversal function

Write a function called preorderTraversal that takes a node of type TreeNode | null. If node is not null, push node.name to result, then recursively call preorderTraversal on node.left and node.right.

DSA Typescript

class TreeNode {
    name: string;
    left: TreeNode | null;
    right: TreeNode | null;

    constructor(name: string) {
        this.name = name;
        this.left = null;
        this.right = null;
    }
}

const grandparent = new TreeNode("Grandparent");
const parent = new TreeNode("Parent");
const child = new TreeNode("Child");

grandparent.left = parent;
parent.left = child;

const result: string[] = [];

// Write preorderTraversal function here
// Your code here

Hint

Use a function that checks if the node is not null, then adds the name to result, then calls itself on left and right children.

4

Run traversal and print result

Call preorderTraversal with grandparent as argument. Then print the result array joined by spaces using console.log(result.join(" ")).

DSA Typescript

class TreeNode {
    name: string;
    left: TreeNode | null;
    right: TreeNode | null;

    constructor(name: string) {
        this.name = name;
        this.left = null;
        this.right = null;
    }
}

const grandparent = new TreeNode("Grandparent");
const parent = new TreeNode("Parent");
const child = new TreeNode("Child");

grandparent.left = parent;
parent.left = child;

const result: string[] = [];

function preorderTraversal(node: TreeNode | null): void {
    if (node !== null) {
        result.push(node.name);
        preorderTraversal(node.left);
        preorderTraversal(node.right);
    }
}

// Call preorderTraversal and print the result
// Your code here

Hint

Call the traversal starting from grandparent and print the names joined by spaces.