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

Tree Traversal Inorder Left Root Right

📖 Scenario: You have a simple family tree where each person can have a left child and a right child. You want to visit each person in a special order: first the left child, then the person, then the right child. This is called inorder traversal.

🎯 Goal: Build a small tree using nodes, then write code to visit and print the nodes in inorder (left, root, right) order.

📋 What You'll Learn

Create a TreeNode class with value, left, and right properties

Create a tree with exactly 3 nodes: root with value 1, left child with value 2, right child with value 3

Write a function called inorderTraversal that visits nodes in left-root-right order

Print the values of nodes in inorder traversal separated by spaces

💡 Why This Matters

🌍 Real World

Tree traversal is used in many real-world tasks like searching family trees, organizing files, or evaluating expressions.

💼 Career

Understanding tree traversal is important for software developers working with data structures, databases, and algorithms.

1

Create TreeNode class and build the tree

Create a class called TreeNode with a constructor that takes a value (number) and sets left and right to null. Then create three nodes: root with value 1, root.left with value 2, and root.right with value 3.

DSA Typescript

# Your code here

Hint

Define the class with value, left, and right. Then create the root and assign left and right children.

2

Create an array to store traversal results

Create an empty array called result to store the values of nodes visited during inorder traversal.

DSA Typescript

class TreeNode {
    value: number;
    left: TreeNode | null;
    right: TreeNode | null;

    constructor(value: number) {
        this.value = value;
        this.left = null;
        this.right = null;
    }
}

const root = new TreeNode(1);
root.left = new TreeNode(2);
root.right = new TreeNode(3);

# Your code here

Hint

Use const result: number[] = []; to create an empty array for storing values.

3

Write the inorder traversal function

Write a function called inorderTraversal that takes a node of type TreeNode | null. If the node is not null, first call inorderTraversal on node.left, then push node.value to result, then call inorderTraversal on node.right.

DSA Typescript

class TreeNode {
    value: number;
    left: TreeNode | null;
    right: TreeNode | null;

    constructor(value: number) {
        this.value = value;
        this.left = null;
        this.right = null;
    }
}

const root = new TreeNode(1);
root.left = new TreeNode(2);
root.right = new TreeNode(3);

const result: number[] = [];

# Your code here

Hint

Use recursion: visit left child, then current node, then right child.

4

Run inorder traversal and print the result

Call inorderTraversal with root as argument. Then print the result array values joined by spaces using console.log(result.join(' ')).

DSA Typescript

class TreeNode {
    value: number;
    left: TreeNode | null;
    right: TreeNode | null;

    constructor(value: number) {
        this.value = value;
        this.left = null;
        this.right = null;
    }
}

const root = new TreeNode(1);
root.left = new TreeNode(2);
root.right = new TreeNode(3);

const result: number[] = [];

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

# Your code here

Hint

Call the function with root and print the result array joined by spaces.