Kth Smallest Element in BST in DSA Go - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to perform an inorder traversal of the BST.

DSA Go

func inorder(root *TreeNode, result *[]int) {
    if root == nil {
        return
    }
    inorder(root.Left, result)
    *result = append(*result, root.Val)
    [1](root.Right, result)
}

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

Ainorder

Bpostorder

Cpreorder

Dtraverse

Attempts:

3 left

💡 Hint

Common Mistakes

Using preorder or postorder traversal instead of inorder.

Forgetting to call the function recursively on the right child.

The inorder traversal visits the left subtree, then the root, then the right subtree. So the recursive call on the right subtree must be inorder.

2fill in blank

medium

Complete the code to return the kth smallest element from the inorder traversal result.

DSA Go

func kthSmallest(root *TreeNode, k int) int {
    result := []int{}
    inorder(root, &result)
    return [1]
}

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

Aresult[k]

Bresult[len(result)-k]

Cresult[k-1]

Dresult[0]

Attempts:

3 left

💡 Hint

Common Mistakes

Using result[k] which is off by one.

Using result[len(result)-k] which gives kth largest, not smallest.

The kth smallest element is at index k-1 because slice indices start at 0.

3fill in blank

hard

Fix the error in the recursive inorder traversal to avoid modifying the result slice incorrectly.

DSA Go

func inorder(root *TreeNode, result *[]int) {
    if root == nil {
        return
    }
    inorder(root.Left, result)
    *result = append(*result, root.Val)
    [1](root.Right, result)
}

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

Ainorder

Bpostorder

Cpreorder

Dtraverse

Attempts:

3 left

💡 Hint

Common Mistakes

Passing slice by value causing no changes to original slice.

Using wrong traversal function in recursive call.

The function should use a pointer to the slice to modify the original slice. The recursive call must be inorder to continue traversal.

4fill in blank

hard

Fill both blanks to create a map of word lengths for words longer than 3 characters.

DSA Go

lengths := map[string]int{}
for _, word := range words {
    if len(word) [1] 3 {
        lengths[word] = [2]
}
}

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

A>

B<

Clen(word)

Dword

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>' causing wrong filtering.

Assigning word instead of its length in the map.

We check if word length is greater than 3 and then store the length in the map.

5fill in blank

hard

Fill all three blanks to create a filtered map with uppercase keys and values greater than 0.

DSA Go

filtered := map[string]int{}
for k, v := range data {
    if v [1] 0 {
        filtered[[2]] = v
    }
}

for key := range filtered {
    newKey := [3]
    filtered[newKey] = filtered[key]
    delete(filtered, key)
}

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

A==

B>

Ck

Dstrings.ToUpper(k)

Attempts:

3 left

💡 Hint

Common Mistakes

Using '==' instead of '>' causing no filtering.

Using wrong variable for key transformation.

We filter values greater than 0, keep original keys for assignment, then create uppercase keys.