Trie vs Hash Map for Prefix Matching in DSA Javascript - Interactive Comparison Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to insert a word into the Trie.

DSA Javascript

function insertWord(root, word) {
  let node = root;
  for (let char of word) {
    if (!node.children.has(char)) {
      node.children.set(char, [1]);
    }
    node = node.children.get(char);
  }
  node.isEnd = true;
}

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

A{}

Bnew Set()

C[]

Dnew Map()

Attempts:

3 left

💡 Hint

Common Mistakes

Using an array or object instead of Map for children.

Not initializing children for new nodes.

Each node's children is a Map to store next characters and their nodes. So we create a new Map for a new child.

2fill in blank

medium

Complete the code to check if a prefix exists in the Trie.

DSA Javascript

function startsWith(root, prefix) {
  let node = root;
  for (let char of prefix) {
    if (!node.children.has([1])) {
      return false;
    }
    node = node.children.get(char);
  }
  return true;
}

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

Aprefix

Bnode

Cchar

Droot

Attempts:

3 left

💡 Hint

Common Mistakes

Using the whole prefix instead of the current character.

Using the node or root instead of the character.

We check if the current node's children has the current character from the prefix.

3fill in blank

hard

Fix the error in the Hash Map prefix search function to correctly check prefixes.

DSA Javascript

function hashMapStartsWith(map, prefix) {
  for (let key of map.keys()) {
    if (key[1]prefix) {
      return true;
    }
  }
  return false;
}

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

AendsWith(

BstartsWith(

CindexOf(

Dincludes(

Attempts:

3 left

💡 Hint

Common Mistakes

Using includes or indexOf which check anywhere in the string.

Using endsWith which checks the end of the string.

To check if a key starts with the prefix, use the startsWith method.

4fill in blank

hard

Fill both blanks to create a Trie node and mark the end of a word.

DSA Javascript

function createNode() {
  return {
    children: [1],
    isEnd: [2]
  };
}

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

Anew Map()

Bfalse

Ctrue

D{}

Attempts:

3 left

💡 Hint

Common Mistakes

Setting isEnd to true on creation.

Using an object or array instead of Map for children.

A Trie node has children as a Map and isEnd initially false.

5fill in blank

hard

Fill all three blanks to build a Hash Map from words and check prefix existence.

DSA Javascript

function buildHashMap(words) {
  const map = new Map();
  for (const word of words) {
    map.set(word, [1]);
  }
  return map;
}

function checkPrefix(map, prefix) {
  for (const key of map.keys()) {
    if (key.[2](prefix)) {
      return [3];
    }
  }
  return false;
}

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

Atrue

BstartsWith

Dfalse

Attempts:

3 left

💡 Hint

Common Mistakes

Returning false instead of true when prefix matches.

Using wrong string method for prefix check.

We store true for each word in the map. To check prefix, use startsWith and return true if found.