Trie Node Design and Initialization in DSA Javascript - Practice Problems & Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of Trie Node Initialization

What is the output of the following JavaScript code that initializes a Trie node and prints its properties?

DSA Javascript

class TrieNode {
  constructor() {
    this.children = {};
    this.isEndOfWord = false;
  }
}

const node = new TrieNode();
console.log(JSON.stringify(node));

A {"children":null,"isEndOfWord":false}

B {"children":{},"isEndOfWord":true}

C {"children":[],"isEndOfWord":false}

D {"children":{},"isEndOfWord":false}

💡 Hint

Look at how the children property is initialized and the default value of isEndOfWord.

The TrieNode constructor initializes children as an empty object and isEndOfWord as false. So the JSON string reflects these values.

❓ Predict Output

intermediate

Trie Node Children Property Type

What will be the output of this code snippet that checks the type of the children property in a Trie node?

DSA Javascript

class TrieNode {
  constructor() {
    this.children = {};
    this.isEndOfWord = false;
  }
}

const node = new TrieNode();
console.log(typeof node.children);

A "null"

B "object"

C "array"

D "undefined"

💡 Hint

Remember what type JavaScript returns for objects and arrays.

In JavaScript, typeof an object literal returns 'object'. Arrays are also objects but typeof returns 'object' for them too, not 'array'.

❓ Predict Output

advanced

Adding a Child Node to Trie Node

What is the output after adding a child node with key 'a' to the children of a Trie node and printing the children keys?

DSA Javascript

class TrieNode {
  constructor() {
    this.children = {};
    this.isEndOfWord = false;
  }
}

const node = new TrieNode();
node.children['a'] = new TrieNode();
console.log(Object.keys(node.children));

A ["children"]

B []

C ["a"]

D ["isEndOfWord"]

💡 Hint

Check what keys are present in the children object after adding a new child.

After adding a child node with key 'a', the children object has one key 'a'. Object.keys returns an array of keys.

🧠 Conceptual

advanced

Purpose of isEndOfWord in Trie Node

What is the main purpose of the isEndOfWord property in a Trie node?

A To mark the end of a complete word in the Trie

B To store the number of children nodes

C To hold the character value of the node

D To indicate if the node has any children

💡 Hint

Think about how a Trie distinguishes between prefixes and complete words.

The isEndOfWord boolean marks if the path to this node forms a complete word stored in the Trie.

❓ Predict Output

expert

Output After Multiple Insertions in Trie Node

Given the following code that inserts characters into a Trie node's children, what is the output of printing the children keys of the root node?

DSA Javascript

class TrieNode {
  constructor() {
    this.children = {};
    this.isEndOfWord = false;
  }
}

const root = new TrieNode();
const word = 'cat';
for (const char of word) {
  if (!root.children[char]) {
    root.children[char] = new TrieNode();
  }
}
console.log(Object.keys(root.children));

A ["c", "a", "t"]

B []

C ["cat"]

D ["t"]

💡 Hint

Each character is added as a separate child key if it does not exist.

The loop adds each character as a separate key in the root's children. So keys are 'c', 'a', and 't'.