Left Side View of Binary Tree in DSA Go - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to initialize the queue with the root node.

DSA Go

queue := []*TreeNode[1]

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Aroot

Bnil

Cnew(TreeNode)

DTreeNode{}

Attempts:

3 left

💡 Hint

Common Mistakes

Initializing queue with nil or empty node instead of root.

Using new(TreeNode) which creates an empty node, not the root.

We start the level order traversal by adding the root node to the queue.

2fill in blank

medium

Complete the code to append the first node's value of the current level to the result.

DSA Go

result = append(result, queue[[1]].Val)

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Alen(queue) - 1

B1

C0

Di

Attempts:

3 left

💡 Hint

Common Mistakes

Using index i which changes inside the loop.

Using last index instead of first.

The first node in the queue at the start of each level is at index 0.

3fill in blank

hard

Fix the error in the loop condition to process all nodes at the current level.

DSA Go

for i := 0; i < [1]; i++ {

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Alen(queue)

BlevelSize

Ccap(queue)

Dlen(result)

Attempts:

3 left

💡 Hint

Common Mistakes

Using len(queue) which changes during the loop.

Using cap(queue) which is capacity, not length.

We process exactly levelSize nodes at each level to avoid mixing levels.

4fill in blank

hard

Fill both blanks to add left and right children to the queue if they exist.

DSA Go

if node.[1] != nil {
    queue = append(queue, node.[2])
}

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ALeft

BRight

Cleft

Dright

Attempts:

3 left

💡 Hint

Common Mistakes

Using uppercase Left or Right which do not exist.

Mixing left and right fields incorrectly.

In Go, struct fields are case-sensitive; left and right are lowercase.

5fill in blank

hard

Fill all three blanks to complete the function returning the left side view of the binary tree.

DSA Go

func leftSideView(root *TreeNode) []int {
    if root == nil {
        return [1]
    }
    result := []int{}
    queue := []*TreeNode{root}
    for len(queue) > 0 {
        levelSize := len(queue)
        result = append(result, queue[[2]].Val)
        for i := 0; i < [3]; i++ {
            node := queue[0]
            queue = queue[1:]
            if node.left != nil {
                queue = append(queue, node.left)
            }
            if node.right != nil {
                queue = append(queue, node.right)
            }
        }
    }
    return result
}

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A[]int{}

B0

ClevelSize

Dnil

Attempts:

3 left

💡 Hint

Common Mistakes

Returning nil instead of empty slice.

Appending wrong index from queue.

Looping wrong number of times.

Return empty slice if root is nil; append first node at index 0; loop levelSize times.