Trie Node Design and Initialization in DSA C++ - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a pointer array for 26 lowercase English letters in the TrieNode class.

DSA C++

class TrieNode {
public:
    TrieNode* children[[1]];
    bool isEndOfWord;
    TrieNode() {
        isEndOfWord = false;
        for (int i = 0; i < [1]; i++) {
            children[i] = nullptr;
        }
    }
};

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

A26

B25

C52

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using 25 instead of 26, which misses one letter.

Using 52 which is for uppercase and lowercase combined, but here only lowercase is needed.

The English lowercase alphabet has 26 letters, so the children array size must be 26.

2fill in blank

medium

Complete the constructor to initialize the isEndOfWord flag to false.

DSA C++

TrieNode() {
    isEndOfWord = [1];
    for (int i = 0; i < 26; i++) {
        children[i] = nullptr;
    }
}

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

Afalse

Btrue

CNULL

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Setting isEndOfWord to true by mistake.

Using NULL or 0 which are not boolean values.

When a TrieNode is created, it should not mark the end of a word, so isEndOfWord is false.

3fill in blank

hard

Fix the error in the loop that initializes children pointers to nullptr.

DSA C++

for (int i = 0; i < [1]; i++) {
    children[i] = nullptr;
}

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

ANULL

B26

Cchildren.size()

D25

Attempts:

3 left

💡 Hint

Common Mistakes

Using 25 which misses the last child pointer.

Using children.size() which is not valid for raw arrays.

The loop must run 26 times to cover all children pointers for letters 'a' to 'z'.

4fill in blank

hard

Fill both blanks to declare a TrieNode pointer and initialize it to nullptr.

DSA C++

TrieNode* [1] = [2];

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

Aroot

Bnullptr

CNULL

Dnew TrieNode()

Attempts:

3 left

💡 Hint

Common Mistakes

Using NULL instead of nullptr (older style).

Initializing with new TrieNode() instead of nullptr.

We declare a pointer named root and initialize it to nullptr to indicate it points to nothing initially.

5fill in blank

hard

Fill all three blanks to create a new TrieNode and assign it to root, then mark it as not end of word.

DSA C++

root = [1];
root->isEndOfWord = [2];
for (int i = 0; i < [3]; i++) {
    root->children[i] = nullptr;
}

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

Anew TrieNode()

Bfalse

C26

Dtrue

Attempts:

3 left

💡 Hint

Common Mistakes

Setting isEndOfWord to true by mistake.

Using wrong number for children count.

Not creating a new TrieNode object.

We create a new TrieNode object, set isEndOfWord to false, and initialize all 26 children pointers to nullptr.