Frequency Counter Pattern Using Hash Map in DSA Python - Build from Scratch

Frequency Counter Pattern Using Hash Map

📖 Scenario: You are working in a library to keep track of how many times each book title has been borrowed. This helps the library know which books are popular.

🎯 Goal: Build a program that counts how many times each book title appears in a list of borrowed books using a hash map (dictionary).

📋 What You'll Learn

Create a list called borrowed_books with exact book titles given.

Create an empty dictionary called frequency_counter to store counts.

Use a for loop to count how many times each book appears in borrowed_books.

Print the frequency_counter dictionary to show the counts.

💡 Why This Matters

🌍 Real World

Libraries, stores, and websites often count how many times items are used or bought to understand popularity.

💼 Career

Knowing how to count frequencies with hash maps (dictionaries) is a basic skill for data analysis, software development, and many programming jobs.

1

Create the list of borrowed books

Create a list called borrowed_books with these exact book titles in order: 'Harry Potter', 'The Hobbit', 'Harry Potter', '1984', 'The Hobbit', 'The Hobbit'.

DSA Python

# Create the list borrowed_books with the exact titles
# Your code here

Hint

Use square brackets [] to create a list and put the book titles as strings inside, separated by commas.

2

Create the frequency counter dictionary

Create an empty dictionary called frequency_counter to store the count of each book.

DSA Python

borrowed_books = ['Harry Potter', 'The Hobbit', 'Harry Potter', '1984', 'The Hobbit', 'The Hobbit']
# Create an empty dictionary called frequency_counter
# Your code here

Hint

Use curly braces {} to create an empty dictionary.

3

Count the frequency of each book

Use a for loop with variable book to go through borrowed_books. Inside the loop, update frequency_counter to count how many times each book appears.

DSA Python

borrowed_books = ['Harry Potter', 'The Hobbit', 'Harry Potter', '1984', 'The Hobbit', 'The Hobbit']
frequency_counter = {}
# Use a for loop to count each book's frequency
# Your code here

Hint

Check if the book is already a key in the dictionary. If yes, add 1 to its count. If no, set its count to 1.

4

Print the frequency counter dictionary

Print the frequency_counter dictionary to show the count of each book.

DSA Python

borrowed_books = ['Harry Potter', 'The Hobbit', 'Harry Potter', '1984', 'The Hobbit', 'The Hobbit']
frequency_counter = {}
for book in borrowed_books:
    if book in frequency_counter:
        frequency_counter[book] += 1
    else:
        frequency_counter[book] = 1
# Print the frequency_counter dictionary
# Your code here

Hint

Use print(frequency_counter) to display the dictionary.