Binary Tree Node Structure in DSA Go - Practice Problems & Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of Inorder Traversal on Binary Tree

What is the output of the inorder traversal on the given binary tree?

DSA Go

package main

import "fmt"

type Node struct {
    Val   int
    Left  *Node
    Right *Node
}

func inorder(root *Node) {
    if root == nil {
        return
    }
    inorder(root.Left)
    fmt.Print(root.Val, " -> ")
    inorder(root.Right)
}

func main() {
    root := &Node{Val: 1}
    root.Left = &Node{Val: 2}
    root.Right = &Node{Val: 3}
    root.Left.Left = &Node{Val: 4}
    root.Left.Right = &Node{Val: 5}
    inorder(root)
    fmt.Print("null\n")
}

A 4 -> 2 -> 5 -> 1 -> 3 -> null

B 4 -> 5 -> 2 -> 3 -> 1 -> null

C 1 -> 3 -> 2 -> 4 -> 5 -> null

D 1 -> 2 -> 3 -> 4 -> 5 -> null

💡 Hint

Inorder traversal visits left subtree, then node, then right subtree.

Inorder traversal visits nodes in the order: left child, current node, right child.

For the given tree, the order is 4, 2, 5, 1, 3.

❓ Predict Output

intermediate

Output of Preorder Traversal on Binary Tree

What is the output of the preorder traversal on the given binary tree?

DSA Go

package main

import "fmt"

type Node struct {
    Val   int
    Left  *Node
    Right *Node
}

func preorder(root *Node) {
    if root == nil {
        return
    }
    fmt.Print(root.Val, " -> ")
    preorder(root.Left)
    preorder(root.Right)
}

func main() {
    root := &Node{Val: 1}
    root.Left = &Node{Val: 2}
    root.Right = &Node{Val: 3}
    root.Left.Left = &Node{Val: 4}
    root.Left.Right = &Node{Val: 5}
    preorder(root)
    fmt.Print("null\n")
}

A 2 -> 4 -> 5 -> 1 -> 3 -> null

B 4 -> 2 -> 5 -> 1 -> 3 -> null

C 1 -> 2 -> 4 -> 5 -> 3 -> null

D 1 -> 3 -> 2 -> 4 -> 5 -> null

💡 Hint

Preorder traversal visits node first, then left subtree, then right subtree.

Preorder traversal visits nodes in the order: current node, left child, right child.

For the given tree, the order is 1, 2, 4, 5, 3.

🔧 Debug

advanced

Identify the Error in Binary Tree Node Initialization

What error will this code produce when trying to create a binary tree node?

DSA Go

package main

type Node struct {
    Val   int
    Left  *Node
    Right *Node
}

func main() {
    var root Node
    root.Val = 1
    root.Left.Val = 2
}

A compilation error: cannot assign to struct field

B runtime error: invalid memory address or nil pointer dereference

C no error, code runs successfully

D compilation error: missing type declaration

💡 Hint

Check if the Left pointer is initialized before accessing its fields.

The Left pointer is nil by default and not initialized to point to a Node.

Accessing root.Left.Val causes a runtime nil pointer dereference error.

🧠 Conceptual

advanced

Number of Nodes in a Full Binary Tree of Height h

What is the total number of nodes in a full binary tree of height h (where height is number of edges from root to deepest leaf)?

A 2^h

B 2^h - 1

C 2^(h+1)

D 2^(h+1) - 1

💡 Hint

A full binary tree doubles nodes at each level plus one root.

A full binary tree has nodes count = 2^(height+1) - 1.

Height h means h edges, so levels = h+1.

🚀 Application

expert

Resulting Tree Structure After Insertions

Given an empty binary search tree, insert the values in this order: 10, 5, 15, 3, 7, 12, 18. What is the inorder traversal output?

A 3 -> 5 -> 7 -> 10 -> 12 -> 15 -> 18 -> null

B 10 -> 5 -> 3 -> 7 -> 15 -> 12 -> 18 -> null

C 18 -> 15 -> 12 -> 10 -> 7 -> 5 -> 3 -> null

D 5 -> 3 -> 7 -> 10 -> 15 -> 12 -> 18 -> null

💡 Hint

Inorder traversal of a BST outputs sorted values.

Inserting values in BST order and then inorder traversal outputs sorted values.

The sorted order is 3, 5, 7, 10, 12, 15, 18.