Height of Binary Tree in DSA Go - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to return 0 when the node is nil.

DSA Go

func height(node *Node) int {
    if node == [1] {
        return 0
    }
    return 1
}

Drag options to blanks, or click blank then click option'

Anil

B0

Cnode

Dtrue

Attempts:

3 left

💡 Hint

Common Mistakes

Returning 1 instead of 0 for nil node

Using 0 instead of nil in condition

When the node is nil, it means the tree or subtree is empty, so height is 0.

2fill in blank

medium

Complete the code to recursively calculate the height of the left subtree.

DSA Go

leftHeight := height([1])

Drag options to blanks, or click blank then click option'

Anil

Bnode.right

Cnode

Dnode.left

Attempts:

3 left

💡 Hint

Common Mistakes

Using node.right instead of node.left

Passing node instead of node.left

To find the height of the left subtree, call height on node.left.

3fill in blank

hard

Fix the error in the code to return the maximum height between left and right subtrees plus one.

DSA Go

return [1](leftHeight, rightHeight) + 1

Drag options to blanks, or click blank then click option'

Amin

Bsum

Cmax

Davg

Attempts:

3 left

💡 Hint

Common Mistakes

Using min instead of max

Adding heights instead of taking max

The height of a node is 1 plus the maximum height of its left and right subtrees.

4fill in blank

hard

Fill both blanks to calculate left and right subtree heights correctly.

DSA Go

leftHeight := height([1])
rightHeight := height([2])

Drag options to blanks, or click blank then click option'

Anode.left

Bnode.right

Cnode

Dnil

Attempts:

3 left

💡 Hint

Common Mistakes

Using node for both blanks

Using nil instead of child nodes

To get heights of left and right subtrees, call height on node.left and node.right respectively.

5fill in blank

hard

Fill all three blanks to complete the height function using recursion and max function.

DSA Go

func height(node *Node) int {
    if node == [1] {
        return 0
    }
    leftHeight := height([2])
    rightHeight := height([3])
    return max(leftHeight, rightHeight) + 1
}

Drag options to blanks, or click blank then click option'

Anil

Bnode.left

Cnode.right

Dnode

Attempts:

3 left

💡 Hint

Common Mistakes

Not checking for nil node

Using node instead of node.left or node.right

The function returns 0 if node is nil, otherwise recursively calculates left and right subtree heights and returns the max plus one.

Practice

1. What does the height of a binary tree represent?

easy

A. The number of children of the root node

B. The total number of nodes in the tree

C. The number of leaf nodes in the tree

D. The number of edges on the longest path from root to a leaf

Solution

1. Step 1: Understand the definition of height in a binary tree

   The height is the longest path from the root node down to the farthest leaf node, counted by edges.

2. Step 2: Compare options with the definition

   Only The number of edges on the longest path from root to a leaf correctly describes the height as the number of edges on the longest root-to-leaf path.

3. Final Answer:

   The number of edges on the longest path from root to a leaf -> Option D

4. Quick Check:

   Height = longest root-to-leaf edges [OK]

Hint: Height counts edges, not nodes, from root to deepest leaf [OK]

Common Mistakes:

• Confusing height with total nodes
• Counting nodes instead of edges
• Thinking height is number of leaves

2. Which Go function signature correctly defines a recursive function to find the height of a binary tree node?

easy

A. func height(root Node) string

B. func height(root *Node) int

C. func height(root *Node) bool

D. func height(root Node) float64

Solution

1. Step 1: Identify correct parameter and return types for height function

   The function should accept a pointer to a Node and return an integer representing height.

2. Step 2: Match options with correct signature

   func height(root *Node) int matches: func height(root *Node) int. Others have wrong parameter types or return types.

3. Final Answer:

   func height(root *Node) int -> Option B

4. Quick Check:

   Pointer input and int output for height [OK]

Hint: Height returns int; input is pointer to Node [OK]

Common Mistakes:

• Using value instead of pointer for root
• Returning wrong data type like bool or string
• Incorrect function parameter types

3. What is the output of this Go code snippet that calculates the height of a binary tree?

package main

import "fmt"

type Node struct {
    left, right *Node
}

func height(root *Node) int {
    if root == nil {
        return 0
    }
    leftHeight := height(root.left)
    rightHeight := height(root.right)
    if leftHeight > rightHeight {
        return leftHeight + 1
    }
    return rightHeight + 1
}

func main() {
    root := &Node{
        left: &Node{},
        right: &Node{
            right: &Node{},
        },
    }
    fmt.Println(height(root))
}

medium

A. 3

B. 2

C. 4

D. 1

Solution

1. Step 1: Analyze the tree structure

   The root has left child (leaf) and right child with its own right child (leaf). The longest path is root -> right -> right, which has 3 nodes and 2 edges.

2. Step 2: Calculate height as edges + 1

   The function returns 1 + max height of children. The longest path has 2 edges, so height = 3.

3. Final Answer:

   3 -> Option A

4. Quick Check:

   Height counts edges + 1 for nodes [OK]

Hint: Count longest path edges + 1 for height [OK]

Common Mistakes:

• Counting nodes instead of edges
• Ignoring nil child nodes
• Confusing left and right subtree heights

4. Identify the bug in this Go function that calculates the height of a binary tree:

func height(root *Node) int {
    if root == nil {
        return -1
    }
    leftHeight := height(root.left)
    rightHeight := height(root.right)
    if leftHeight > rightHeight {
        return leftHeight + 1
    }
    return rightHeight + 1
}

medium

A. Returning -1 for nil node causes incorrect height calculation

B. Missing base case for leaf nodes

C. Using pointers incorrectly for root

D. Not handling empty tree separately

Solution

1. Step 1: Check base case return value

   The function returns -1 for nil nodes, which causes height to be off by one compared to standard definition.

2. Step 2: Understand correct base case for height

   Height of empty tree should be 0 or 0 edges; returning -1 leads to negative heights and incorrect results.

3. Final Answer:

   Returning -1 for nil node causes incorrect height calculation -> Option A

4. Quick Check:

   Base case should return 0 for nil [OK]

Hint: Base case for nil must return 0, not -1 [OK]

Common Mistakes:

• Returning -1 instead of 0 for nil
• Confusing base case with leaf node
• Not adding 1 after recursive calls

5. Given a binary tree where each node stores an integer, write a recursive Go function to find the height of the tree and also return the sum of all node values at the deepest level. Which approach correctly combines these tasks?

hard

A. Use iterative BFS to find height and sum nodes at last level in one pass

B. Calculate height first, then traverse tree again to sum deepest level nodes separately

C. Use a recursive function that returns both height and sum at deepest level by comparing left and right subtree results

D. Use recursion to sum all nodes and ignore height calculation

Solution

1. Step 1: Understand combined task requirements

   We need height and sum of nodes at deepest level in one function efficiently.

2. Step 2: Evaluate approaches

   Use a recursive function that returns both height and sum at deepest level by comparing left and right subtree results uses recursion returning height and sum together, avoiding multiple traversals.

3. Step 3: Compare other options

   Calculate height first, then traverse tree again to sum deepest level nodes separately does two traversals, less efficient. Use iterative BFS to find height and sum nodes at last level in one pass is valid but iterative BFS is not recursive. Use recursion to sum all nodes and ignore height calculation ignores height, so incomplete.

4. Final Answer:

   Use a recursive function that returns both height and sum at deepest level by comparing left and right subtree results -> Option C

5. Quick Check:

   Combine height and sum in one recursive pass [OK]

Hint: Return height and sum together recursively to avoid extra traversal [OK]

Common Mistakes:

• Doing two separate traversals
• Ignoring sum at deepest level
• Using iterative approach when recursion asked