Count Words with Given Prefix in DSA Javascript - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the problem 'Count Words with Given Prefix' ask you to do?

It asks you to count how many words in a list start with a specific prefix string.

beginner

Which JavaScript string method helps check if a word starts with a given prefix?

The startsWith() method returns true if a string starts with the specified prefix.

beginner

How can you count words with a prefix using a simple loop in JavaScript?

Loop through each word, use startsWith(prefix) to check, and increase a counter if true.

intermediate

What is a Trie and how can it help in counting words with a prefix?

A Trie is a tree-like data structure that stores words by their letters. It can quickly find how many words share a prefix by traversing the prefix path.

intermediate

Why is using a Trie more efficient than checking each word individually for large datasets?

Because a Trie stores common prefixes once, it avoids repeated checks and can count prefix matches faster than scanning all words.

Which JavaScript method checks if a string starts with a specific prefix?

A startsWith()

B includes()

C indexOf()

D substring()

The startsWith() method returns true if the string begins with the given prefix.

What is the main task in 'Count Words with Given Prefix'?

A Count words that start with the prefix

B Count words that contain the prefix anywhere

C Count words that end with the prefix

D Count words that have the prefix in the middle

The problem requires counting words that start exactly with the given prefix.

Which data structure is best for efficient prefix searches?

A Stack

B Trie

C Array

D Queue

A Trie stores words by prefixes, making prefix searches very efficient.

If you have 1000 words and want to count prefix matches, what is a simple approach?

A Sort the words alphabetically

B Reverse each word and check suffix

C Use a stack to store words

D Use a loop and startsWith() for each word

Looping through each word and checking with startsWith() is a straightforward method.

What does the startsWith() method return if the prefix is empty string?

A false

B undefined

C true

D throws error

An empty string is considered a prefix of any string, so startsWith('') returns true.

Explain how you would count words starting with a given prefix using JavaScript.

Think about checking each word one by one.

Describe what a Trie is and how it helps with prefix counting.

Imagine a tree where each branch is a letter.